Windows 11 cumulative update improvements: an overview

Hello, 

In 'Reduced download size' part, devices moving from M1 cumulative update to M2 cumulative update. In this senario, I would like to know when installing M2 CU, will the device go back to RTM and then update to M2 CU or go from M1 CU directly? Will the RTM base version as an intermediate state as well? If yes, I'm confused where does these forward deltas(File1 v2, File2 v2, File3 v3) comes from since they are not in M2 CU?   Thanks in advance.