I mean if max out the the shared fates you get more items in a shop that has a mount that requires alot of those gems to get.
Sharlayan Diadema-800 gemstones glamour piece
Bicolor Gemstone Voucher -100 gemstones u need about 500 vouchers for a mount and per someone math "500 vouchers each, = 50,000 gemstones, = 3,572 FATE completions!"
or if you want to get all the music as well barding etc.
So yeah any boost will help with that
+1 for make it happen se