It looks like CDW, at least, sells by the individual license, to judge from the search results at that link. Top one is "Windows 10 Enterprise LTSC 2019 - upgrade license - 1 license".
If you were supporting multiple users in a small business environment definitely make sure you buy as many Windows SKUs as you have end users to be compliant, however.
All of this becomes moot once you have >25 clients; then you can transition to using volume licensing and it's essentially unlimited. It still tracks it though and Microsoft can ask to look at it, especially if you change from Open to Select or some other volume pricing agreement, so keep that in mind.