Yeah, there can be a problem there, but the causes are MANY.
For a start, the taper beyond the widest part can affect the tip of your toe. Look at those pointy street shoes for example (especially lady's shoes!).
Second, when they measure your foot with a Brannock device, they often do so on a bare foot or with only a thin sock. Fine, but you may be wearing a thick wool sock in the field, which has not been allowed for.
Third, some brands of shoes seem to differ from the Brannock device anyhow. They use a seriously different last, or they just don't conform. Or the factory gets the mould slightly wrong so the shoes are all undersize.
Fourth, and this is the killer: your feet will grow at least one length/width in the field over what is measured in the store. This alone can cripple you. If you are a 10D in the shop with thick walking socks, buy a 10.5 E fitting. Yep: up in both length and width. As I mentioned in the article, shoes which are slightly too big are not much of a problem compared to shoes which are too small.
Fortunately, if you experiment by buying end-of-run joggers from the web sites which specialise in them (heavily discounted), you can usually afford to experiment a bit in shoe sizes. It is worth doing so.
PS: yes, mostly true to size.