Actually it is safer to set the final expected flight level on the pressurization panel, since in this case you cannot forget to modify it during the climb. The only downside of this is that cabin altitude reach its final value at the beginning of the first cruise part instead of when reaching the final cruise level.
Take a look at this paragraph from FCOM:
Investigation of pressurization incidents in the fleet has indicated that some
operators are setting the FLT ALT before takeoff to an intermediate altitude and
then resetting the FLT ALT one or more times during climb until the final cruise
altitude or flight level is reached.
So, if we disregard the possibility that some operators used this as MCP ALT during climb (which I highly doubt), there clearly were pressurization incidents when using the "reset FLT ALT" technique during step climbs, so Boeing decided to strongly recommend setting final cruise level on the pressurization panel.