The new app just dropped that *partially* addresses this... It looks like if there is an ethernet/wired backbone, that the app will tell you 1000 vs 100 vs 10 Mbps each eero has to the LAN.  It does *not* alert you if the speed falls, if it switches to Wireless, or any bandwidth measurements per unit.

In fact, if I had to guess, it is just reporting  the current speed negotiated on the wire between each eero and the nearest upstream switch.