I don't know if it's wise to disconnect using a relay/contactor while under load.
If you must do this under load, you should use a proper DC breaker with an arc chute, that will pull the arc away from the contacts while the power is being broken.
Higher voltages have a longer arc, so it may be a larger problem when disconnecting PV while under load.
I personally put my AIO inverter into mains only charging mode, before turning off the PV DC breaker. This way the SCC ramps down (and possibly disconnects its internal PV relay).
I need to turn off the DC breaker between inverter and batteries, I make sure there is no charging/discharging going on before doing this (by changing inverter settings, like changing to UTI).
This should increase the lifespan of the breaker contacts and minimize arcing dangers.