I did the same thing. The relator told us that she stopped taking calls after our offer. If this isn't a sign that you shouldn't trust realtors I don't know what is.
But getting 1-3% of the delta on a higher offer that doesn't exist yet is not only a meaningless money difference, if it slows the deal down it costs them money.
Now if they could get a stronger offer by still keeping it on market, and they're only the listing agent, then yes a new offer of like 50k more isn't going to mean that much for them. They'd rather get it sold. That is messed up too because that delta is meaningful for the owner.
From what the parent said, they stopped taking calls because they wanted to represent both sides. It's fucked up.