In London you're more likely to expected to filter, it's part of making progress, although I don't think they'd mark you down for it as you're considered a novice, hence why they don't like you positioning to near the left or right for general riding, yet you get taught more extreme positioning if you do an advanced course.
But back to filtering, you can do it on test, but same as any other exercise, you'd carry out observations and only proceed if it's safe to do so.
Whole point of having a bike is to make better progress, you just need to make sure it is safe, and have a B plan in case something changes, or if in doubt, show restraint.