This is, I believe, the only context in which flashing amber appears here in the UK - it’s on pedestrian crossings, and it means ‘you may proceed if the crossing is clear of people’ - it is accompanied by a simultaneous flashing green signal to the pedestrians, which indicates ‘continue crossing if you have started, but don’t begin crossing’.
There is discussion about switching some regular junctions to flashing amber at quiet times of the day - so drivers could give way to one another, but there are concerns that might just not work as it relies on everyone being equally cautious.
Having driven in Korea a lot, I like their system for left turns at intersections with stop lights. There, you cannot turn left unless you have a green left arrow. There’s no judgement call if it’s safe to turn left. You either have right of way, or you don’t turn left.
There are some exceptions where a sign is posted permitting unguarded left turns. Those tend to be where less trafficked streets intersect.
You would think that, but around where I live they’re actually adding flashing yellow left arrows to intersections that already had green left arrows. So it’s an increased cost. There’s often a sign next to it saying something like “left turns yield to pedestrians”. I think it’s part of an initiative to increase pedestrian safety.
They’ve already added bikes lanes to most of the major streets.