There are some commands where it doesn't work, in some cases '/' is interpreted as an option prefix and the failure is obvious, for other commands failures are not so obvious (copy IIRC, cost me half an hour some time ago)
This is the most frustrating part. cd? Fine with forward slashes! mkdir? Shits a brick! robocopy? No problem with either. xcopy? Better have backslashes. There is no consistency and sometimes, yes, the failures aren't an immediate error or will produce strange behaviour (especially if they look like flags).
So the path forward should be: MS goes bash only in its documentation, to the point that people forgets about cmd with the exception of those that really have to deal with legacy stuff. But what about powershell, does it need \ or can it use / safely?