Extreme bummer..
So no it isn't and it seems all the forum crawling I've been doing doesn't seem to give any hope to those wanting a Raspberry Pi 4 to do frame packed 3D MVC formatted files.
I saw a mention of LE 9.2.6, but no conclusive evidence that it does beyond half frame TAB/SBS 3D.
Suppose I'll give it a try on my RPi400 and cross my fingers...