Updated 11112023-181747
I still haven't been able to find it mentioned anywhere in the documentation (big surprise!,) so I'm not sure which version of iOS 17 for sure introduced this change, but my device is currently on: iOS 17.2 (21C5040g)
...and I just discovered with delight that ^Taping a message now offers the tapback response buttons in a compact row above the context menu.
A screen capture demonstration with audio commentary of how tapback functionality responds in iOS 17.2 to the Control+Tap keyboard shortcut.