Tier 2+ maps dropping in delves?

Just got an iceberg map at delve depth 90. Is this intentional? Previously non-map areas have only been able to drop tier 1 maps, even high-level areas like the eternal labyrinth.

I occasionally get map drops from regular delve content, I even got a t13 not long ago. I am not entirely sure (since my build is an aoe clusterfudge) but I wonder if they can drop from destructable objects like vases. I have also had some drop from the loot pinata phase of delve, I haven't noticed a correlation with the type of delve. The content that "obviously" should drop maps in delve is chart-type chests in map delve or vaal/abyssal outpost areas but these other drops do seem to happen, whether intentional or not.

aaaaaand what mob is depth 90? i don't think everyone has that kind of information memorized yet

Monster level was 69. It's high enough for T3 maps to drop from magic or rare enemies if level was the only thing that mattered. But I've never seen higher than T1 maps drop outside maps (with the exception of shaped T1 maps in the eternal labyrinth) and last I checked delve wasn't a map.

ok
well uber lab can drop t6 maps because it drops shaped t1 maps. also, delve is an exception, as far as i can tell.
uber lab chests can also give you upwards of t13, tho not sure if thats the highest. and delve chests can give guardian maps.