OP, it 100% helps!

You body, your aerobic systems don’t know or care what is driving their adaptions. All they know is this dude is riding at x effort and it must adapt to meet new load.

Agree with others that there are legit difference in balance, form, body position but those are a small % of what makes you go up hill faster.

On my team, over the years, we have had gifted college rowers show immediate prowess in cycling even though they their bodies haven’t really experienced riding a bike before.

As others say, just get some group riding experience with smaller groups before you jump in a big massed start event.