I think Phoenix having clearer policies regarding this would be helpful. In my experience this hasn't been true. I have 2 channels that have been at 0 sat each for months, but they're both a few thousand sats of capacity each (I did a stupid and accidentally sent too much to Phoenix, opening another channel), so I'm guessing ACINQ isn't interested in closing these channels at the current feerate.

I would imagine having larger amounts going unused would lead to ACINQ wanting to put that liquidity elsewhere though, so YMMV