This is a blatant conflict of interest. My god.
Generally agents steer well clean of that, for legal and time reasons.
A realtor is there to put properties in front of you / put your properties in front of others, and then close the deal when you tell them which property you're interested in.
Volume pays realtors, not price-over/under-replacement.
There are other details that come up through a transaction that many people wouldn't even think about. Are appliances included? Window treatments? Leftover paint? What year the transaction closes could impact taxes or incentives for either party. Inspections (what types of inspections are permitted, their timeline, what will be repaired prior to sale).
If there are disagreements about any of those, or if the property was materially misrepresented by the selling agent, it's way more messy than if another agent is involved and it's clear who represents who.
Your realtor (as the seller) is now going to give preferential treatment to one buyer for their own personal gain.
So they're only preferring whoever is bitching the loudest?
If people are out there just doing what their agents say with no questions asked, well, then yeah probably insist your agent doesn’t represent the other party too.
Needless to say, I probably got some preferential treatment since, if the transaction closed, the seller's realtor gets double the commission.
It's called "dual agency" and I think it's illegal in some states (for good reasons). When realtors are acting as a dual agent, representing both buyer and seller, there are strict rules they're supposed to follow to prevent a conflict of interest, but in practice it's difficult to make sure everyone is playing fair. I'm pretty sure the seller needs to sign a consent form with their realtor in order for them to represent both sides of the transaction.
In hot markets this is a way people often get an advantage as a buyer: tell the selling agent you want to use them as your agent too, so they get the whole 6% if the seller picks your offer. So if the bids end up being close, the agent ends up lobbying for you (or lobbying you to make your offer closer).
Some selling agents refuse to do this because it's pretty shady, but definitely not all.
I've also heard of similar things including negotiating down the selling agent's cut as part of it but haven't seen as much of that firsthand.