It has been my experience. My agent took a particular likening to me for whatever reason, probably because I'm a very low drama client, and took me around on the open houses that are mostly intended for agents to connect. In my town these happen on Wednesday morning. Selling agent usually has some basic amenities out like a coffee station, pastries, occasionally pizza. A large number of agents just cruise through continuously. It's something of a festive atmosphere. I was usually the only client vs agent in these situations, and while all agents have a degree of salesmanship to what they do, I saw first hand very frank discussions of potential problems that would cause a deal to feel sour after it was done.

As an agent you make your money on the overall volume, not squeezing the last bit out of any particular deal. Near as I can tell getting a reputation for deception is nearly career suicide unless you're at the very low end of the market. I think you're making a fundamental mistake in thinking about incentives in the context of a single sale vs having a career in a business that is very strongly driven by personal networking. This is a common fallacy in microeconomic thinking.

My observation where I live is that there are somewhat exclusive networks and not everybody is in the same one -- they might be clustered around catering to a clientele speaking a particular foreign language, for instance, and be somewhat apart from more "mainstream" agents. Anyway, I personally watched the selling agent try and convince me and my agent that the water damage in a property I was looking at was hardly damage at all and anyway, it doesn't rain in California, so don't worry about it. Sure, that's just an anecdote. So is your story, though.

I don't doubt that two agents who had frequently worked with each other amicably might be more frank, but I do doubt that agents all, or even mostly, presumptively do this with every counterparty they meet.