At night your cycle MUST have white front and red rear lights lit. It MUST also be fitted with a red rear reflector (and amber pedal reflectors, if manufactured after 1/10/85). White front reflectors and spoke reflectors will also help you to be seen. Flashing lights are permitted but it is recommended that cyclists who are riding in areas without street lighting use a steady front lamp.
https://www.gov.uk/guidance/the-highway-code/rules-for-cycli...
In old times, police cars would have rotating lights, and I found those much easier to track. So if one uses flashing lights, there should also be some constant level of light to make positioning of the source easier.
Just spent a minute imagining my cat with his eyes brightly blinking on and off just before he jumps onto my cluttered desk and knocks things over, or starts rubbing up against my feet trying to trip me up; then sadly realised you meant cars...
Vehicles that need to be seen like police, fire, paramedic, road safety, all have flashing lights. Indeed cats have flashing lights to use when they're causing a hazard.
I suspect you're right WRT difficult to estimate distance/approach speed for vehicles with only a flashing light, but not sure about combinations of constant and intermittent lights.
Bonus: in UK cyclists may use flashing lights but only on clothing IIRC, at least they need separate constant lights on their bicycles.