There is no need for misspelled versions of a tag. As the tag has now been removed (and is not used by any question), it will get deleted in some time.
Also, as we are following the policy of having plural tags, disassemblers created.
I had a look at the IDA website, and the software comes in three versions as stated in the question, freeware, IDA Starter and IDA Professsional. IDA seems to be the correct tag that encompasses all these. Hence, ida is now the master tag. idapro is the synonym.
I havent retagged the idapro questions as of now.
Poof! They are gone.
On a serious note, that is normal behavior. Those questions were tagged with ida before the synonym relation to idapro was made. Tag synonyms affect future associations, whereas past tagging needs to be handled explicitly/manually. I just did the retags.