General question: Doesn't your realtor have a vested interest in NOT trying their hardest to negotiate down a price if they're paid off comission?

Question: If both my realtor and the seller's agent are commission based and get more money if the price of the home is higher, how do I know that my realtor actually tried his hardest to attack a price for us?

This is a general question regarding real estate as a whole and not an indication or accusation against my specific realtor. I'm just a curious and skeptical person by nature so this is me just curious about an off-thought that came across my head during negotiations.

Context: We offered 30k under asking on a house in the upper $700s. It quite honestly was arbitrary why we went 30k under and it was the realtor that suggested we went with that price, so there wasn't a "goal" that my realtor was trying to get such as if our budget was maxed out or something. Like literally any money off was a win for us and technically a loss for my realtor since we were going to go through with it anyway. There was no "I have to hit this price or I'll lose this sale" aspect.

Seller came back at 10k under asking with some additional negotiations but we eventually agreed upon 15k under asking. Then the inspection came through with some items and the realtor suggested going for a $3k credit so we can fix the stuff on our own. The overall story of the negotiation and how my realtor fought for our interests across the board was very entertaining and I have no reason to believe he didn't fight for us BUT doesn't fighting for us mean he gets less of a paycheck??? I mean is it possible that the story was really fluffy and he didn't actually fight as hard since he subconsciously (or consciously) meant he'd get paid less if he fought more?

In the future, should I hold my cards closer to my chest when it comes ot the realtor and be a little less flexible on the price? Am I a crazy person for wondering this? Is it possible he called the seller's agent like "hey my client wants 30k under but can we just agree to like 15k under so we both make more money here?"

Restating that I don't think my realtor didn't fight for our best interest but it's really just a question of what to watch out for and if this happens often or something.