Agreed...you were lumping the two together. The application as expressed lead to the following:
225.39(D) All Others. For all other installations, the feeder or branch-circuit disconnecting means shall have a rating of not less than 60 amperes.
Assuming the engineer provides the calculated load calculation in accordance with Art.220 the disconnection means aspect of your question is answered again in 225.39 (D).
Comments based on the 2017 National Electrical Code.
*All code responses are based on the 2017 National Electrical Code[NEC]