I intentionally asked this question now, because a reviewer to one of my manuscripts insisted that solar simulator lamp mostly gives UV. My manuscript was rejected (from a very highly respectable journal) based on the reviewer's judgement.
The solar simulators I have used all had some filters to make the lamp spectrum be closer to the standard AM1.5 spectrum. Without the filters, a lamp often has too strong emission in UV... That might (or might not!) be what the reviewer was meaning.