Openreach DLM shouldn't react to a single power down even if its a power cut not safe shutdown.
Just one power outage can effect the users stats
CHRY have had plenty of abrupt power outages over 2 years with VDSL2 active and with the stats also running could see the negative result.
I used to just find the torch and find the offending equipment which caused the trip switch to activate and isolate it then flick the trip into the on position that would have taken less than 7 minutes and hey ho the VDSL2 stats have been hit hard.
What I do now is to remove the 12V power plug from VDSL2 modem and flick the trip and wait 30 minutes before inserting the 12V power plug back into VDSL2 modem and stats have not been effected.
So in theory you could turn off the fibre modem 48 times in a 24 hour period as long as you wait 30mins before powering it up and the DLM will be none the wiser.
PS I am not going to test my above theory as do like a good nights sleep