Steps to reproduce: - Create an item - Choose no source of classification - Save the item - Re-open the item for edit => FAIL: the $2 is set to the default (DefaultClassificationSource)
Confirmed this is the behavior in 19.05.
This doesn't sound wrong to me - if you don't set any default classification source it will cause problems with cn_sort - so it makes sense to enforce the default if nothing is selected. Maybe the subfield should be made mandatory by default?
Still appears to be intended behaviour for me :) Please reopen if you disagree!