Asking participants not to screen record or take screenshot was standard practice at every company I’ve worked at where we discussed anything like financials or sensitive business plans.
Many people still take screenshots of things they think are useful. Things still get shared though emails and occasionally posted on social media.
I have worked with various secure chamber VPN and VNC systems that make it quite difficult to record or screenshot. These are companies where their IP is worth billions of dollars and everyone wants a piece of it. It's difficult enough that it's not worth the effort to try and work around it. The rare time I really need something for debugging, I'll take a photo with my cameraphone, but it rarely comes to that.
Because it's that much harder, I record a lot less of it. Likewise for all the other engineers I work with. Friction won't stop it entirely, but it will make it far less frequent.
That you think the only attack vector here is a 3rd party device means you haven't really considered everything. Consider screenshots that might happen for many reasons, including malicious software, or even normal software someone might be using, and accidental exposure.