Maybe it's just the way you phrased point 4, but "Avoid using the development sharpening controls of Lightroom" is missing the important words "for output sharpening". The "makes more sense..." comment implies he did actually recommend a typical 3 phase input/creative/output sharpening.
yeah, this sounds like a guy that may know quite a bit about printing, but seems perhaps a little clueless about the entire post processing pipeline.
There are 3 parts to sharpening, and LR development module primarily addresses capture sharpening. Yes you can crank it up, but really shouldn’t.
This doesn’t have much to do with output sharpening, which is what he is talking about.
Perhaps there are a lot of “experts" on the internet in various forums that are clueless or still buy into outdated stuff. I assume since you asked the questions, you feel this forum is an exception to that ...
still a pretty stupid thing to say. I would ask him if that applies to the stuff he puts on the internet?