Just off the top of my sleepy head:
Both Ryan Hall and Cosmas Ndeti ran really really slow half marathons right before their Boston PRs. There are lots of examples of runners running really slow before busting big ones. If this was the best Webb could do, don't you think he would have a sense that it was and, thus, not be racing?
Hopefully Webb doesn't come to this site, or, if he does, he's motivated by the posts on here.
Thirty years ago the top marathoners raced a lot of relatively minor road races, sometimes pretty darn slowly, for lots of reasons: They were part of their training - or, just to make some money, or, they just liked to race. At the height of his powers, Bill Rodgers ran 52:45 for 10 miles finishing third at Bobby Crim in 1977. Sure it was hot that day, but, 52:45?! Luckily, back then, there weren't a bunch of kids on the internet busily posting about how Rodgers was washed up. There were lots posting about Ryan before Boston last year. Ryan ran great at Boston (whatever you think about the wind, he beat a lot of top guys that day).
Webb may yet toe the line in the Olympic finals this year. Patience.