It might work for you, but your 'advice' is vague and poor. And to be honest looks like you just posted a random comment in a thread to try and needle
@MHB, as it is totally unrelated to the topic or what is normal water profiles for most lagers (exception below).
So there is ~4gm CaSO4 per level US teaspoon*. In Aus we use the Imperial teaspoon and tablespoon measurements.
There are 3 Imperial teaspoons per 1 Imperial tablespoon**
There are 1.2 Imperial teaspoons per 1 US teaspoon**
So your tablespoon full of gypsum = 4 x 1.2 x 3 = 14.4gm of CaSO4. That means for your double batch you added 28.8gm of CaSO4 (assuming each was level). What was your double batch volume and initial Ca and SO4 levels? Cause that is a fair wack of CaSO4. According to Brewersfriends calculations even if you use RO water at 0ppm of either, that amount raises 70L of water to 96ppm Ca and 230ppm SO4. Definitely Burtonising your water, but what that has to do with the OP or any other comment in this Lager thread is beyond me. Or are you just trying to provoke MHB?
The generalised comment re 1 tablespoon or 14.4gm in a lager is poor as it gives the same levels of 96ppm Ca & 230ppm SO4 (assuming it is single batch water volume of 35L, but lets face it many brewers would use less than that for a 23L brew). Even half that is way too much for most lagers and that assumes the brewer has access to RO water and then wants 0ppm chloride to balance out the SO4. All SO4 in any lager would be unbalanced and likely make it taste ****. Qualifying your statement with "you probably don't need a whole one" is vague.
There are a couple of lagers that use higher mineral water, Dortmund water being something that might fit what you suggest, but again who asked about making water to suit a Dortmunder and again the advice would be incomplete as there would need to be some Calcium Chloride (CaCl2), Sodium Bicarbonate (NaHCO3) and Magnesium Sulphate (Epsom salts MgSO4) added at varying amounts. And even then that would be assuming the brewer has RO water, which most don't.
*
How to brew teaspoon CaSO4 link
**
Teaspoon & tablespoon conversions
EDIT - Oh yeah and a little bit of education for you
@hoppy2B utilization of sulphur from sulphate by brewers yeast has been known about for a long time. But it can easily use sulphur from other sources and
does. You no longer need to suspect, now you know.