Minecraft allows items with "fake" enchantment glint without them having an actual enchantment - one of the ways to do this is with the command:

/give @p baked_potato{Enchantments:[{}]}

(not necessarily a Baked Potato, can be any material). Another way is with a plugin.

But when running a COMPLETELY fresh run of latest SpigotMC the glint doesn't show.

I tested this on both the latest Spigot and latest Vanilla servers - on Spigot it doesn't show the glint and on Vanilla it does - the NBT tag is maintained though (images attached).

P.S: for all those that say: "Why are you doing this?! Just apply some random enchantment and add a HIDE_ENCHANTS flag!", I say: I have MANY reasons why I do it this way (cuz of plugins - there, I said it) so please don't suggest that as a "fix".