This is beyond silly. You could be using your phone to factcheck something that relates to the ongoing discussion. Or having a side-chat with another member, privately expressing/requesting an opinion to provide context. Or to take quick notes. Or, nowadays, you might even be using an AI to keep a running summary of what the speaker has been rambling about in the last 50 minutes, translated from 'buzzspeak' to 'human…
You call it silly because you could be doing useful stuff on your phone. I'd go one step further and say that even if you're slacking off that's not necessarily a bad thing. Everybody, including politicians, slacks off from time to time. Be it due to stress, awful sleep because the neighbor's dog barked all night, illness, or something else. It's just human and there's little wrong with it as long as you do your job…
While I agree, the legislation that the politicians passed says the opposite it true.