Hi Rahul,
I would say that it does not make sense to fix accruals of interest before key migration date, as usually you are resetting these on the next business day, so it means that in a common scenario TPM44 is not part of legacy data migration activities.
to answer your question - if you run TPM44 with no immediate posting, then no acctual postings will be recorded in your books, these Update types get status 'ToF - to be fixed' - then the flows have to be posted later using corresponding transaction TPM10.
on the other hand, TBB1_LC is applicable for the migration scenarios, when you need to mark certain flows of transactions as posted (in SAP TRM subleger) without actually generating financial documents.
hope this will help you.
Kind regards,
Renatas