When creating an alert for the BlockBreakEvent in versions past v1.20.0, it is only able to output air.

The test done is breaking 4 diamond ore and one stone block.
Debug report for 1.21.0:
https://bin.scarsz.me/627199b0-648d-4753-964d-fcd48fbcc4cf#rep39Te2cah6ccyOMoeOYegQ5l4oMtmn
Debug report using 1.20.0 without refreshing configs or anything:
https://bin.scarsz.me/bb0b3603-9f1b-4f26-b627-b5d29a477548#UIGkVcalo8XYbaOeiEHBrd4ubHY2jW1s

Hypothesized in the discord #support chat that this is due to switching to using asynchronous threads. Other alert triggers such as BlockPlaceEvent or PlayerJoinEvents still work fine in the later versions.