Its been rumoured that Sigma refuse to reverse engineer for mirrorless and that they’ll only produce glass on mounts for which they have protocols provided to them by the OEM. I would guess that Sigma don’t want a situation where their emount glass has licensed support and the AF has near/matching native level performance but RF is reverse engineered and the AF is noticeably inferior compared to native RF glass.
Remember Tamron, Zeiss, Tokina and Voigtländer haven’t supported the RF mount yet either.
Zeiss and Voigtlander don't even require any new protocols! No AF. That means they could essentially build in an adapter and use EF protocols they already have.
Samyang/Rokinon HAVE made RF glass, even some that does AF. How did they do it? Using EF protocols? China has a reputation for ignoring patents and intellectual property, so it could also be that they got a copy of the RF protocols and used it without license.
I suppose everyone is different, but what you mention is fully a non-issue for me. Once the lens is on, you don't even notice the adapter is there. If you are changing between EF lenses, you just push a different button for the lens release. Its almost fully transparent. The weight is negligible, and while you can measure than an RF equivalent would be an inch or two shorter and a couple of ounces lighter, in practice what you are using is not any larger or heavier than it was on a DSLR. I sometimes feel that people who say things like this about the adapter just haven't really tried it. Of course I'm sure there are people who shoot differently than I do, and maybe they are changing multiple lenses very often.It's the extra size and weight + have to carry the adapter too. When you have a small lens, the adapter adds significant extra size.