It is one of the plausible solutions to Apple's device identifier problem:
M4 Macs
Mac16,1 MBP 14” M4
Mac16,2 iMac 24” M4 (2-port)
Mac16,3 iMac 24” M4 (4-port)
Mac16,4 DNE
Mac16,5 MBP 16” M4 Max (384b & 512b)
Mac16,6 MBP 14” M4 Max (384b & 512b)
Mac16,7 MBP 16” M4 Pro
Mac16,8 MBP 14” M4 Pro
Mac16,9 Mac Studio M4 Max (last unconfirmed device)
Mac16,10 Mac mini M4
Mac16,11 Mac mini M4 Pro
Mac16,12 MBA 13” M4
Mac16,13 MBA 15” M4
So far there are no other Mac16's BUT the latest OS did include a reference to:
Mac17,1
Mac17,2
indicating that 17th generation Macs will launch before the new OS. These could be M5 Studio and M5 Mac Pro. However with the rumors around Hidra it could be M4.5 or be something new like "P1" for Pro chip 1. Or it could be that Apple is launching some M5 hardware before the next macOS release that isn't the Studio or Pro and 16,14 and 16,15 identifiers will be found in the next OS release. I view that as the least likely, but it's possible.