It seems that when Jean was being created, Chris’s finger must have slipped and he entered the wrong key into her gene sequence. This has screwed up Jean’s ability to control her power forever, and cannot be fixed, ever. So her suckyness is ENTIRELY HIS FAULT.

Yeah...

Now you might think accidentally pressing the wrong key is a trivial human mistake – and you’re right! — but the thing is, Chris is a 12,000 year old Elemental. He has not made such a noob-ish error for 6,000 years, (literally!) and he’ll never make it again after (conceivably). This fact is such a big deal that it is unquestionably the most significant event happening in this timeframe, comparatively with all other timeframes.