Tyrannical means " Unjust or oppressive governmental power.", so the justification for the mandate is important, not just the fact that a mandate exists.
A mandate with a good justification is authoritarian but not tyrannical.
A mandate with a good justification is authoritarian but not tyrannical.
The forcing of wearing masks is a tyrannical action, whether it's for a 'good cause' or not.
Some people view the ends do not justify tyrannical means.