On my reading, this is the exact same problem, not the exact opposite problem. The break-even bar for a reasonable monolith is a lot lower than for microservice

On my reading, this is the exact same problem, not the exact opposite problem. The break-even bar for a reasonable monolith is a lot lower than for microservices, so the GP's question is specifically asking, under a hypothetical where the team simply uses a monolith, what benefits the team would miss out on relative to microservices. If there are none, or they aren't relevant to the project scenario, then microservices probably isn't justifiable. (I, too, am in the position of pushing back against microservices for hotness' sake.)