While there is no IG penalty ; it's also an OCD problem for iLv rounding and/or blu-ing your stuff.

I get that the subweapon stats were "not planned" ; but that's a fake excuse after SB.
"Oh noes, you'd have +500 gathering that would break a lv.50/60 fish ; the +3000 from the rest of your lv90 gear is fine".

If you want an objective downside to the lv.61 jig : FSH get a penalty for spiritbonding since you get IV/V instead IX/X for the subweapon. it's both a waste of potency and inventory slot