It is - shield use was originally it's own seperate sub-class called
'Sentinel' (or 'SEN' for short) in the original launch version of FFXIV version 1.0, where shields could be equipped to GLA, THM and CNJ, that class's 'class rank' would gain SP when a shield was equipped to any of those classes, but SEN abilities could only be used when a shield was equipped to GLA. SEN as an actual class was scrapped completely when the battle system was redesigned circa patch 1.20 in preperation for the addition of Jobs, and shield use became classless, with SEN's abilities being given to GLA/PLD by default (but again could only be used if a shield was equipped). This resulted in a legacy of level 1 to 50 having certain shields that could be used still by CNJ/WHM and THM/BLM, with single-handed wands and rods respectively for those classes (even Y'shtola used a single-handed wand originally).
Because ARR has the ability for old 1.0 players to transfer their 1.0 character data into ARR with all their previous levels and EXP available, that requires that old legacy to be present in the new game to prevent errors occuring. So it's not going to be removed I'm afraid, as SE will not throw 1.0 players under the bus like that again, given it was continuing 1.0 player support that allowed ARR's development in the first place.
As for the FFXIII CNJ/WHM and THM/BLM weapons being converted to two-handed weapons, again I doubt SE will do this as they've never gone back and changed old event gear to accomodate changes to the battle system (you also have to remember that the FFXIII gear is actually
not 'glamour gear' - it's level 13 not not level 1, and has very good stats for that level, some of the best low level gear in the game - this is because it was originally added to ARR before the glamour system was added.
Although it would be nice to see them make adjustments to the FFXIII gear (including adding new gear for new classes and Jobs added to the game since then), I don't see it happening I'm afraid.