Not all breakers with handle ties are NON-COMMON TRIP...i.e. 'individual trip''
Common trip is where all poles are opened together when a fault or overload happens.
Some quads etc where the 2 middle poles are for 240v loads will be common trip,and the 2 outside poles of 120v will be non-common trip.[INDIVIDUAL TRIP]Quad requires 2 spaces
Other 2 pole ,240v breakers with two handles and a tie will also be common trip...where overcurrent in one leg will open both poles inside the breaker.
Some of these designs are merely for the mfg convenience and economy
The usual TANDEM/TWIN DUAL breakers with a couple single poles will be individual trip also...even with handle ties.
and...These will not provide two poles for 240v loads!
..a common error.
These SP tandems are for 120v loads only .Tandem One pole breakerBreaker Requires one space
There are also double tandems ..'Quad tandems'
.. with 4 handles that take two spaces like a 2P20a/2P30a
There are also 4 handle breakers and with 'ties' in one package that are used as main breakers and are COMMON TRIP!
Switching a breaker of manually is not the same as trip.
A breaker that is tripped open [off] due to over current or overload,,, is tripped ..not switched!
The moral of the story....
the life you save may be mine!