Between December and January: UI changes, library updates and stake donations. You need to remember that jbg is on XSPEC from June. What happened between June and December? Nothing. He said he was working on 1.4, let's see when 1.4 is out if there are commits for that between June and March which takes into account 7 (Jun/March excluding Jan/Feb) months of development.

Do another check: check for any core changes on the blockchain logic, you'll not find any. Only UI changes and library updates, in 9 months of work full time, plus who knows what the other claimed developer is doing.

Also his real name is not the one you mentioned.