That ruling is indeed still accurate. The rules for how the game determines which enters-the-battlefield replacement effects are applied do not apply to turned-face-up replacement effects like the Hydra's.
As such, a manifested
Hooded Hydra that is turned face-up while under the effects of a card like
Turn to Frog or
Polymorphist's Jest will not receive any +1/+1 counters, because it will not have the ability that would normally grant it those counters once it's turned face-up.