Damage in salvage run

It takes forever to advance in salvage run. I saw a video somewhere that claimed you can fasten that if you allow the grots to multiply. Does that actually work?

I played a lot of rounds where I don't kill any grot, let them summon as much as possible and clear everything in the last two rounds. That gives me about 4k damage.

The last few days I had less time and killed everything as fast as possible and still did about 4k damage per run.

Does the trick work and I just had some bad rng or can I speed run through it and ignore summons?