Unlikely, they actually sold several oscilloscopes in other form factors before.
If you take all the critical chips out of an oscilloscope, remove the silicon dice from their encapsulation, you still take up more area than any smartwatch. Just the main processor is typically larger than an Apple watch. On top of that you need 1-2 ADC chips of a similar size, several hundred MB of RAM chips, a ton of discrete components that form the very sensitive frontend, then you also need a battery and a display, ports, and mounting hardware.
This is like saying Intel has been selling i7 processors for decades, so they should be able to pack it into a watch.
Packing an oscilloscope into a watch is several orders of magnitude more complex than you seem to think. Oscilloscopes of any configuration are many orders of magnitude more complex than you imply here.
This is the website where you can see the product line up: https://www.gabotronics.com/
Of course this isn't a full featured oscilloscope, it never promised to be one.
I think you’re overestimating the functionality of this smartwatch.
They didn’t really make a full oscilloscope with hundreds of megabytes of RAM and high sample rates and many effective bits of precision.
They just used a microcontroller with a built-in ADC and exposed those ADC inputs with some input protection and filtering. Yes it’s more than a watch, but making a simple oscilloscope out of a micro with an ADC is a relatively simple EE project. It’s often done as a small project for EE students.
The real challenge was making a UI, packaging it, and shipping a hardware project to a small number of people.