"CLIMB AND MAINTAIN" used to be in the FAA AIM, when it was an AIRMAN's information manual.
It's still there.
MAINTAIN.
a. Concerning altitude/flight level, the term means to remain at the altitude/flight level specified. The phrase “climb and” or “descend and” normally precedes “maintain” and the altitude assignment; e.g., “descend and maintain 5,000.”
Just reinforces that you're not on a "Cruise" clearance.
