I checked the construction plans for the Boise City bypass (or, to give it its chopblock title, "US 287 Boise City Relief Route") to see whether these were DOT/consultant or contractor errors. The relevant job piece numbers are of the form 13337(XX)--I have 13337(16) and 13337(19) in my collection, but there may have been other contracts which I missed.
Taking Corco's pictures in sequence:
This is a DOT/consultant error (the contractor manufactured the sign faithfully as shown on the plan sheet).
Same as above, except the plan sheet shows the two panels butted together.
Here I refer to the large sign panel, not the route shield assembly ("sign salad") in the foreground. The larger capital letter "A" in "Amarillo" is a contractor error; the plan sheet shows uppercase and lowercase letters in the correct height ratio.
This is a composite DOT-consultant/contractor error. The plan sheet shows a trailblazer assembly using Oklahoma state route shields (meeting the correct standards for such, down to Series B for the digits) instead of the correct US route shields. But it was a contractor decision to use Series D instead of Series B. (Frankly I find it difficult to object because I feel the Series B digits called for in the official standard compromise legibility.)
This is another composite DOT-consultant/contractor error. The layout, as shown on the plan sheet, calls for "JCT" at the overly large size used on this sign (16" for both all-uppercase "JCT" and for capital letters in the primary destination legend--if I were designing this sign and kept the "JCT" legend, which I agree is unnecessary, I would have put it at 12" capital letter height). But it is the contractor's fault that the capital and lowercase letters in the primary destination legend are not in the correct proportions on the actual sign: on the plan sheet they are.
This is partnership between the public and private sector at its finest: what opportunity to screw up the one misses, the other will pick up.