That’s still very much working off the power the spell grants the caster though.
Yeah I’ve never been sold on that. Common English doesn’t say giving someone a thing you’re holding is “dropping it”.
Like, in American Football, if the QB hands the ball to the RB, you wouldn’t say “he dropped the ball”.
Sunbeam isn’t creating an object though: it’s solely creating a spell effect. That’s a big difference to me, at least.
Either way, I’d imagine you could very much end the magic effect of Sunbeam, even if it’s ruled not to be on the caster.