Some temporary tables are very specific in the columns they have and often update using one of those columns as an index. Because of this, it's not possible to use vw_log for all temporaries.
I've gone ahead and added the appropriate steps to the affected importers so that they cleanup temporary data when they're done. I've also added a step to the uninstaller for temporary tables, in case someone doesn't complete an import and uninstalls later. It should be able to detect dynamically named tables that follow a newly enforced naming convention. So from Gamma 5 onwards, temporary tables must be named like 'vw_temporary_*'. I've also added a step to the upgrade that will check if there are pending imports. If there aren't, it will remove any relevant leftover temporary tables. If there are, it will attempt to rename the relevant temporary tables so they follow the new naming convention. This introduces a risk of data loss for any imports were already started before the upgrade but not completed until afterwards, if the temp data is oddly named and therefore might be missed by the upgrade. There's not much we can do about that; I think these measures are quite sufficient.
Marking as fixed in the next release.