I think the problem here is that they submitted a fabrication. If someone is prepared to do that, I don't think how they drafted the document is really the issue.
Reserved concurrency both guarantees a portion of your concurrency limit be allocated to a lambda as well as capping concurrency of that lambda to that portion. Reserved concurrency has no cost associated.
Provisioned concurrency keeps a certain number of execution environments warm for your use. Provisioned concurrency costs money.
See: https://en.wikipedia.org/wiki/List_of_grammar_schools_in_Eng...