OP, if I was renting and found my LL hanging around the property like that I would be pretty furious.
You sign a lease, it's effective from that day. Your LL has absolutely no business being inside the property from that day. If they had things to do there, they should have been taken care of before the keys are handed over!
But, honestly, it's really not worth the stress of making any kind of issue about it. Just keep a record if it and hopefully nothing like that happens again.