Abel starts with a test you can run at your next standup. Ask five people to define the mid-market. You will get five answers, and they will not be close.
The disagreement is not pedantic. It is the symptom. A word that means revenue to one person and headcount to another is not describing a real thing. A go-to-market plan built on it inherits the vagueness. Abel's replacement is two buckets and nothing in between.
The line between them is not size. It is whether the person using your product is the person who signs for it. Abel makes that the load-bearing distinction in a separate conversation, and it explains why you cannot blend the two motions.
When the user and buyer are one person, a good product and a clear landing page can close the deal. When they are two people, someone must carry the case from the person with the pain to the person with the budget. That route runs past legal and procurement. That is a sales motion, and it costs what a sales motion costs. Calling the account mid-market does not make that cost smaller.
So Abel converts the label into a question. Are we at the top of small business, or the bottom of enterprise? Pressed, most teams say the bottom of enterprise. Good. Now you know which game you are playing, and you can staff and price for it.