ritz is capable of 206 flat. maybe a little faster.
however, he has the running style to grind it out which leads to tiring eventually and the last few miles he just can't keep it up. that is why his times are not so good.
so ritz would compete very well if it were a 20 miler.
the challenge, and ritz recognizes this, is to not grind but relax with his running style. this is where mo farah is most superior, he's got a super relaxed yet very aware style where he is consciously saving energy and running efficiently.
the marathon too is such a crap shoot, there is probably one chance in 3 that ritz will be right on the day.
the right day will give a 206. or a 3rd place finish.