600-650mm in a 60 degree arc for the 1991 HA is not unrealistic at all, but is on par with the last batches of the 2A4.
current 2a4 level is also similar to M1A1 (non-HA) and IpM1 in SB, and higher than original M1.
i would also like to remind you that 2289 M1A1's were upgraded to the HA standard, while less than 90 leopard 2A4 received the last batch upgrade. most 2a4's sold by germany to other countries were actually of the older armour standard, and we saw the result of this in turkey.
as such, since the model in-game does not represent last batches of 2a4, and there's such a small number of last batch 2a4s made, its more representative to use the older armour in-game.
besides, there's plenty of mid 1990s leo 2a5 and A6 versions to choose from.