mbtiles copy --bbox do not copy tiles from low level zoom

[RobertSasak]

Lets say I want to create an extract from mbtile using mbtiles copy with bbox parameter. From my tests it copies only tiles from some zoom level while skipping low zoom levels.

What is the logic behind bbox parameter?
It seems like the tile need to be fully inside bbox. Is that correct?

Can perhaps @nyurik author of this feature #1060 comment on the implementation?
Implementation seems to be here https://github.com/maplibre/martin/pull/1060/files#diff-159ced981a64a228577655c70ca8aadd868a9e6a84d9ac5146a4c2f76584a616R605

Thank you.