Do you frequently use applications which, on the fly, change what their keyboard shortcuts are? Like, copy is Cmd+C right now, but five minutes from now, in the same application, it will suddenly be Option-P instead? And Fn-Q ten minutes after that?
If not, why do you assume that an application won't consistently present its contextual touch buttons in the same locations each time it presents them? Because the only case in which you couldn't develop muscle memory for those buttons is one in which they are not in the same location each time the application presents them.
(and if your retort will be that you use different applications which will make different choices for their contextual buttons, well, they probably already used different keyboard shortcuts for application-specific tasks, and you developed muscle memory for those, so...)
If not, why do you assume that an application won't consistently present its contextual touch buttons in the same locations each time it presents them? Because the only case in which you couldn't develop muscle memory for those buttons is one in which they are not in the same location each time the application presents them.
(and if your retort will be that you use different applications which will make different choices for their contextual buttons, well, they probably already used different keyboard shortcuts for application-specific tasks, and you developed muscle memory for those, so...)