some of us have over 64 years of muscle memory about stalks on the steering column and where the turn signal indicators are
It's bad enough that folk's rarely use turn signals, now they have an excuse not to.
I can understand your point, and it made me chuckle.
Working with zero experience using stalk-less or yoke steering, and having a lifetime of experience with stalks and round steering wheels, I can relate.
As a driver, I've made it a practice to always signal prior to moving the wheel. Prior to braking as well when slowing for a turn. Folks who brake before signaling the turn really don't grok the purpose of these communication tools. Signaling first is partly done simply because once you start turning the wheel your hand isn't near the stalk any more and muscle memory is more vague. So, if I can move the stalk before turning, I can move the button before turning too.
The example of a Roundabout being challenging for using a button on a steering wheel at a glance seems legit. Because you may signal one way to enter and another way to exit. But how far will the wheel be turned to follow the course of traffic, a quarter-turn at most? I want to think I could still reach the button and with practice become quite adept at signaling in such a situation.
Over the years I've had to adapt to much more random button placement by manufacturers for cruise control. This is something I use any time I'm on the highway. I prefer to press the "cancel" button rather than tap the brakes to disengage to avoid sending a false braking communication to following traffic. So, the ergonomics designed into the system is nice when it is there. Every model of car seems to put the various cruise buttons in different places, but, I always manage to learn them in each car I've owned.
I don't think having the turn signals on a button would be much different for me to adapt to. Though, I haven't had the opportunity to face that challenge and therefore do not have any hard opinion on it one way or another. Still, I remain hopeful and optimistic about their use being something I could adapt to and enjoy, what with me being a big fan of "the best part is no part" and all that.