TBH, it might just be that it's harder than it appears.
There's been a number of London based man hunts that have shown this. Ones that included significant concentrations of police resources/time (and public/political pressure) yet all that apparent CCTV hasn't translated into being able to track someone through London quickly and accurately.
CCTV is often poor quality, zoomed way out and doesn't provide half the cover people assume. Coverage there is is fragmented between private cameras, businesses and various agencies/councils etc. Physically collecting it (before it gets overwritten) for all potential routes, reviewing, tracking, picking him up after blind spots with branching pathways/doorways is massively labour/time intensive.
Minor attempts at evasion. (A hood/ hat, head down, change jacket, stick to the commuter crowd, duck down blind alleys) might not make someone vanish from CCTV, but it can seriously increase how much of a pain in the arse it is to keep a pin on them, and how much time it takes to pick them back up.
Undoubtedly Police have more information than what is public. But if they had clearer CCTV or further sightings, they'd release it imo. This is a political hot potato and the Met will not want the media to turn from bloody gov let im stay to bloody police can't catch im. Only reason they would hold back that I can think of is they're nearly on top of him, it could provoke/spook him/allies, or they think he's dead.
IMO obviously, flavoured with experience having to actually review CCTV, (not in London though.)