Even fast LACP needs three seconds and that's on the same collision domain.

How does BGP actually detect a link is down? Keep alive default is 30s but that can be changed. If you set it to say one second, is that wise? Once a link is down, that fact will propagate at the speed of BGP and other routing protocols. Recovery will need a similar propagation.

Depending on where the link is, a second can be a "life time" these days or not. It really depends on the environment what an appropriate heart beat interval might be.

Also, given that BGP is TCP based, it might have to interact with other lower level link detection protocols.