This is a very common finding in competition shooters who dry fire their guns a lot pulling through DA on each and every dry shot and cant figure out why their SA shots land low/lateral.
Well, I'm not talking about gaming but serious gun use.
When you have liability and responsibility for your shots fired and your first shot is the most important (and preferably the only shot taken), all these considerations are null.
And it's way easier to train to handle the SA trigger pull than to handle the DA trigger pull, thus the priorization to train the latter. Usually duty gun users have limited budget and time allocated to training (compared to competitive shooters, expecially those that at least partly live off of it and get sponsored, and those that make money by training others). Thus the priorities might be aimed at different parts of the skillset.
And yes, of course you have to train the secondary SA trigger pull at some point, too. But this thread is about his complains of the DA trigger pull.
that is cautioned against by people who are pretty good with TDA guns.
And by that you mean competitive shooters, which is a completely different world than duty pistol users (which the P8A1 happens to be).
You can't and you really shouldn't modulate your grip between the shots so when you practice live, you want to fire at least two in a true DA/SA sequence to train not to overgrip, which is what the DA shot promotes, for the second shot.
YMMV, but in my world and in my experience, it doesn't.
But best way would be to NOT use a DA/SA gun to begin with, which is why the majority of current duty pistols are striker fired with constant trigger pull. Even the Bundeswehr with their P8A1 figured that out and will replace it with a striker fired CZ P13 in the near future.