Normally, I'm quite sympathetic to your excellent questions. This time I'm going to say you've spent too long in front of a computer. Pre-decrement and post-increment are a convenient pairing. Post-decrement and pre-increment are a less convenient pairing. They are somewhat symmetric but not symmetric enough.

While on the topic of hardware stack, the timings annoy me. Some people write 6502 assembly to use zero page when they could use stack. It is easier to prototype an algorithm using zero page and ordering operations to use stack is an extra step in an already complicated process. However, the result allows recursive algorithms - or use of subroutines within interrupt. Even if stack usage were no faster than using zero page, a program which uses stack is smaller because it omits the one byte address operands. However, we are in a situation where stack timings are asymmetrical, there is minimal advantage to using stack, legacy software greatly neglects stack and therefore there is minimal advantage to improving stack timing.

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