Road bike recommendations

It's simple - the rim is smaller and wider than a 700c which gives you enough room to run a big tyre which brings the wheel back to almost the same size as a 700c. Plus you'll usually have room for mudguards as well.

Decided to pump it up and see how it look.

placed it on my Dad's bike, 700c x 25c.

the diameter look quite similar with the 650b x 42c, the 700c is a touch bigger (hard to see).