That is correct.
I would also vote for the points from @r.sander as core restart/sync takes some time for RAW systems.
If you want to calculate what your system can handle i do the following calculation.
Number of cores * 60 seconds → cpu seconds available per minute
Now you look at the time your check_mk services need (take the average) * number of devices → cpu needed to make all checks per minute (if you normal check interval is 1 minute)
If the second value is below the first one then all is fine.