It doesnt matter if it was or wasn't (i personally dont care so not getting involved in this bit of the topic), if its not there anymore, as in its been physically removed from the engine bay, re-piped for non-abs and the bulb is no longer part of the equation, it is not going to fail.
The ruling is to do with ABS >>FITTED<< to a car. Its in line with the other VOSA guidelines such as you can't test rear seatbelts if theres no rear seats/belts etc.

PMSL at people basically saying every RST is going to be banned from the road because we all removed ABS 20yrs ago