ClearScore only tracks Equifax, Monzo shows your score from all 3 major agencies but only tracks your file from Transunion. Both only do weekly updates at the most and monthly at the least.
If you want a true picture, you would need to check Transunion, Equifax and Experian as some companies don’t report to all 3, or there can be some delays between them.
I’m sure I read in this forum that Monzo was looking to improve credit insights by getting the full file from all 3 in, not just the score, but not sure where they are up to with that (if they are still working on it). Until then, you need to check all three seperately, or use something like CheckMyFile that can pull in all 3, in real-time, for a monthly fee.