No this is really not about that, cyclists are always allowed to take up the full lane in cities, but it’s rarely legal to split a lane, and even then it’s a terrible idea.

Preliminary results from a study in the United Kingdom, conducted by the University of Nottingham for the Department for Transport, show that filtering is responsible for around 5% of motorcycle Killed or Seriously Injured (KSI) accidents. (Bicycle statistics are harder to locate.)

I don't think motorcycle data on lane splitting is particularly relevant, because motorcycles are able to keep up with traffic.

If a cyclist can't lane-split, then what are they supposed to do up a hill? If they take the entire lane drivers get annoyed, if they don't take the entire lane (and follow the common guideline of riding as close to the edge as safe and practical) then you claim they are doing the wrong thing too?

Filtering specifically refers to stopepd traffic where there should be minimal differences.

Filtering is not sharrowing. Sharrowing is splitting a large lane into two without a lane.

Filtering is riding on the line between lanes.