At the end of the day the selection bias may not apply in a meaningful way as the type of boomer unable to navigate through a simple multiple choice survey would likely not be using the internet in the first place.
For example my dad is 73 and has never used a computer in his life. Worked as a gardener and never needed it for work. He sends letters to his close ones or lets me or my mom do the typing for him. So there’s 0 chance of him getting scammed.
The younger boomers and older gen X would have likely used computers for about 30 years now so would be much more adapted to it as this point. It’s not the year 2000 anymore