Its not so much the moving over blocking that we are expanding on. Line of fire between two sections of elevated terrain is blocked by blocking terrain on a lower elevation, on an indoor map. If the line of fire is blocked, concievably you would be able to draw line of fire to said blocking terrain

OK, I can see that being confusing: how can it block my LOF if I can't draw LOF to it? And frankly I don't know what to tell you: the blocking is at level 1, so it has to be targeted at that level. It blocking LOF at level 2 is just one of those oddities.

Yes it makes sense, but I don't see any current rules text to support it.

That darn "exists at all levels" line being removed messed this up. As it stands, the blocking terrain only exists on level 1, though it still blocks line of fire as per the LoF rules.

And I'm not sure if "exists" is a good term to use here; it may be better to just call it grounded blocking terrain. We have obvious reasons then why it can't be destroyed in this situation, even though it still blocks line of fire from elevated to elevated.