So for 86 seasons my Australian flat game has never produced a 100% horse, 95 is the max I have seen and they don’t progress as 4yo’s now all of a sudden the same lines are turning out 100% 4yo’s did something change ?

Yes the younger horses were buffed so they could compete with the older horses and so that the people could play a flat only game.

I did post about this but think it got lost in the bar fixation

My trials have massively changed nowadays too. I've not yet seen 100% potential (flat only), but my sprinters were always at 97.5 as 3yos, so I assumed with the flat only disadvantage, this was retrospectively 100. However, my 4yos are suddenly very good, my 3yo horses very rarely win my trials races anymore, but when brought back at 4, can go on to dominate them. Before the change, my 3yo's an 4yo's had very little between them

Not gotten to my 4yo yet but I have noticed some wild trial results like 16l winning margins from horses who then suddenly can’t win a race. Though this does only happen on my main pc where the ck visuals are still glitched.