I came to the opposite conclusion--they removed it to decrease clarity of the rules.Why, then, would they have removed a sentence specifying this? Because that way they don't need to add such a sentence for every other (non-specialized) magic item in the game. It's simply to increase clarity throughout the rules.
That's my read, at least.
Reading the exact same things, I come to a different conclusion.
A plain reading of the (new) wording gives no suggestion that you need to already be a spell caster.
Why, then, would they have removed a sentence specifying this? Because that way they don't need to add such a sentence for every other (non-specialized) magic item in the game. It's simply to increase clarity throughout the rules.
That's my read, at least.
From the discussion we had on Scrolls some time ago, I seem to recall the Starter Set was actually using a later version of the rules than the Basic DM's Guide, so I would go with the Starter Set wording.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.