The fact of a weekend boater not knowing about something tech doesn't surprise me....
An experienced marine professional not knowing about something in his or her field or related fields to me would be very strange.
I don"t know fstbttms personally, but after reading his responses on tech issues as well as political issues involving bottom paints, zinc's, environmental issues, etc...for many years ....I can only surmise he is a well read pro that keeps up in his field. Thus probably knows why ultrasonic cleaners are not common. I don"t clean bottoms and I know why.
To be fair though, in recent years the systems seem to be working better....the jury is still out on just how much. The last Passagemaker article gave them hope, but stated that they certainly don't replace good bottom paint just yet.
I am waiting for my marine engineer friend to email me and reeducate me on what ultrasonic systems for larger boats do work.