Thats why its good for a salesrep to be technical and understand the product and how much work it would take for feature X. If the potential sale is worth the extra eng work then, hell yeah, go ahead and promise the feature.

My last company did that to close some multi-million dollar deals and only took a quarter to build.

I literally just did exactly that half an hour ago.

Of course, it's my company and I'm both the salesperson and engineer, but sometimes you have to sell shit that doesn't exist yet.

I think the issue he's talking about is more along the lines of "hey we promised X _and_ that we could deliver it in Y" when Y is an unreasonable amount of time. Situations like that almost always lead to death marches in my experience.

hopefully you will never see the the salesperson charging into the engineer meeting yelling "I promised the customer 6 months ago that we would ship this feature in 3 months, where the hell is it" at a sea of faces that had clearly never heard of any such thing.