I completely agree. There are similar rules over here about leaving a gap to the kerb, and that there should also be a gap left by overtaking vehicles. Both are often not observed.

Here's the (brief) rules for roundabouts: http://www.highwaycodeuk.co.uk/rules-for-cyclists-roundabout...

Most cycling proficiency courses here in the UK will tell cyclists to ride more centrally when in a narrow lane, which is good advice. A cyclist is also legally allowed to do that.

It gets a bit fuzzy though when there's a cycle lane provided.