Agreed, I think it's a lot harder to hold a proper assertive line when you're going that bit slower, not helped by the fact that slower newer riders are understandably nervous and reluctant to do so. I've seen it for example where obviously beginner riders would rather weave into what are effectively parking spaces so as to continue hugging the kerb, than hold their line (in a position that seems to them like the middle of the road) which would avoid then having to effectively pull back out into traffic when they next meet parked cars which is in itself challenging.
Agreed, I think it's a lot harder to hold a proper assertive line when you're going that bit slower, not helped by the fact that slower newer riders are understandably nervous and reluctant to do so. I've seen it for example where obviously beginner riders would rather weave into what are effectively parking spaces so as to continue hugging the kerb, than hold their line (in a position that seems to them like the middle of the road) which would avoid then having to effectively pull back out into traffic when they next meet parked cars which is in itself challenging.