There seems to be nothing more "controversial" than the topic of "When to season a sous vide protein" during the cook.. If you thought the issues of when to smoke before or after sous vide was bad, I think this one is even worse LOL! As a matter of fact this particular topic got me kicked out of another "Sous Vide" Facebook group that has a very overbearing and arrogant "King" who has made his reputation by beating people over the head with a certain AmazingRibs.com article about marinades to try and prove this flawed point. To me, when you have to resort to an article that does not even address what you are talking about (Sous Vide Cooking) to try and prove a point that makes very little sense OR assumes what other people are thinking, I know you are just parroting what others have told you instead of doing any research of your own.
SO, let's delve into this Very Serious (so some think anyway, LOL) topic and you can figure out on your own how you want to season your sous vide cooks going forward. It is not MY goal to force you to change your ways or even to convince you I am right, but to just bring up some REAL facts and let you decide on your own and keep them in mind the next time it comes up.
FACT A: Most recipes you find in books, online, in app's, and pretty much everywhere have you season your meat BEFORE putting it in the bag for a sous vide cook. Many very prominent Chef's and food experts including Thomas Keller, J Kenji Lopez Alt, Yannick Alléno, José Andrés, Daniel Boulud, and many others season before bagging. As a matter of fact you will be hard pressed to find a published recipe that does not. Do this test, check out as many recipes in books and online as you can and add up the ones that season AFTER the sous vide cook. If it were SUCH a big deal and the "Proper Way" to season for sous vide, you would think most recipes and "Sous Vide" experts would agree and do it this way.
FACT B: Name me ONE other cooking method that you only season the food AFTER it is cooked.. frying, braising, boiling, grilling, smoking, searing, etc all season the protein BEFORE cooking. Sous vide is really just another cooking method. It is different from others as it uses a water bath for precise temperature control, but it is still cooking none the less.
FACT C: Not many people season food thinking that the seasoning will completely "Penetrate" the protein. This is a BIG reason this nonsense gets pushed by some. They assume that people have a false perception that when you season a sous vide cook the seasoning will penetrate all the way through. I personally have never met anyone who thought that who understood anything about cooking. When I bake a ham and I season it before putting it in the oven, or even that big thanksgiving turkey, I know that the seasoning will not penetrate deep into the meat unless I use an injection. But I season it to make the exterior tasty.
FACT D: You cannot use an article about something totally different, like "How Marinades Work" to try and prove your point on why you should not season a sous vide cook before hand. That is like trying to prove why you should not stick your hand into a hot deep fryer by explaining how vegetable oil is made. It makes no sense at all as they are two different things. What would actually make MORE sense is to use the article that explains how "Heat can effect the way Brines are absorbed by proteins " as at least that article has something that can relate directly to sous vide low temperature cooking. That article actually shows that low heat cooking makes the protein absorb the brine faster and better.. Huh, isn't that something.. LOL! Another great article that proves you do not have to penetrate the entire protein to make it taste good is the article on how Smoke Works with meat. Smoke seasons the entire surface and maybe a fraction of an inch into the meat, but it sure makes the entire thing taste delicious!
FACT E: People will always have their own personal preference on how they cook. Me personally, I like to season before cooking sous vide because I know the meat will get uniformly seasoned throughout the surface, and yes the purge will also get seasoned, making it perfect to make a nice sauce with after. Sure I will also add a little more seasoning after it comes out of the bag, but not a huge amount. I am sorry, I don't know anyone who cannot afford the tiny amount of more seasoning I may use by doing this. And, yes I have cooked all different ways and I find I get the best results this way.
In conclusion, feel free to cook the way you like and how you feel produces the best product FOR YOU. BUT please refrain from pushing your ideas on others because of a misquoted article or because of what someone said with no facts to back them up. do some of your own research, testing, and playing around on your own and discover how YOU like to cook. Don't let someone bully you or push you into cooking their way no matter how important they think they are.