HDRP: unexpected fade into existence when creating lights at runtime

with out-of-the-box light settings for an HDRP project, I’m attempting to create spot lights at runtime

I’m doing exactly what this documentation prescribes, and everything renders as expected when executed in Start

however, if I execute that exact same code in a coroutine that has yielded past frame 2 (so frame 3 and beyond), the spot lights fade into existence

any idea what’s going on here?

UPDATE: I believe this was being caused by the exposure settings