https://xtools.wmflabs.org/adminstats/en.wikibooks.org currently displays 0 import actions for every user. However, https://en.wikibooks.org/wiki/Special:Log?type=import&user=Leaderboard lists quite a couple actions for the last month.
Ah, given that for me, everyone had zero imports (see screenshot in the original post), I assume this is the recent action
13:14, 4 June 2021 Leaderboard discuss contribs imported Transwiki:Super Mario Sunshine by file upload (49 revisions) (per WB:RFI) (thank)
since there didn't seem to be any other imports "by file upload" within the last month by this user. That means the import log action isn't quite "non-existent". Is there any way we can count both actions as one?
There are only two types: interwiki and upload. The one you mention was an upload. Both are counted according to AdminStats config: https://github.com/x-tools/xtools/blob/2048dac01a5ff5b541ed4184a8f5a81a2c7cd3e2/config/admin_stats.yml#L62-L64