(RPL) percentage function % not preserving stack level 2

[cdmackay]

Having recently discovered the joys of percentage functions: % and Δ%/%CH on 15C
& 42S (and WP 34S), after years of doing them manually on other calculators or in my head, I
went looking for them on my 50g.

I'm surprised to find that, there, they don't preserve level 2 of the stack in
the way that on earlier calculators they preserved Y, which can be quite useful.

Of course, it's nothing that can't be done manually, or I could assign
≪ SWAP DUP ROT % ≫ to a key/menu (or something more clever, once I work it out).

But am I missing something?

If not, any idea why this changed, with the RPL calculators, compare to e.g. 15C/42S?

thanks very much…