You're right, "sent a strong signal" is deliberately ambiguous, in the sense that there has not been a declared policy shift of the FDIC to protect uninsured deposits. However, given that SVB and Signature were not previously declared Systematically Important Banks, yet all of their depositors were made whole, should give depositors confidence that that the Federal Government will see they are protected.

Now, whether the FDIC should make this a declared policy position remains to be seen, but I believe that would require congressional action.

This was pretty strong: https://home.treasury.gov/news/press-releases/jy1337