No. Good god, man, no.So you are saying that Starengine didn't diverge from Cryengine.
StarEngine diverged from CryEngine at 3.7
LY and CE diverged from one another at 3.8
So, because 3.7 is less that 3.8, StarEngine's changes are as compatible with CryEngine as they are with Lumberyard.
If they'd diverged at 3.7, and StarEngine was based on 3.8, then StarEngine would be based on code that wasn't the same, and there'd be problems.
If you stay with CE, or you switch to LY, taking later updates takes work because of StarEngine's differences. Which is why my quote from yesteryear about not just doing big merges.