Phil-in-MI wrote:
Just a guess on my part:

Portable tools need lightweight motors. The type of motor traditionally
used in circular saws is synchronized to the frequency of the prime AC
power. The only way to change the speed is to change the frequency from
60 Hz to say 40 Hz.

Hmmm... maybe that circular saw needs a VFD (variable frequency drive)
like the ones used in industrial applications. Wow, this saw is starting
to get pretty expensive now. g