AASHTO made major changes to the how the wind load is calculated and the load factors (Strength III Wind load factor was previously 1.4), starting with the 8th Ed., so if the NSBA document is more than 5 years old, it may not be valid for use with the 8th or 9th edition spec.

Anyway, NSBA is recommending load factors that are more conservative than the minimum required by AASHTO. Nothing strange about that. It's also not in conflict with the spec, which uses the wording "not less than 1.25". As it states in the commentary "Often the construction loads are not accurately known at the time of design."

AASHTO doesn't attempt to define what the wind load should be during the various stages of construction, because there are just too many possible permutations. Sometimes, if the combined stresses are too high throwing everything at the erected steel girders, we use a reduced wind load in combination with load of the wet concrete. During the deck pour, and for the 24 hours afterwards, the wind needs to be below 25 mph for the concrete to cure properly, so assuming 70 mph wind during that phase seems reasonably conservative.

I use the AASHTO Guide Spec for Wind Loads on Bridges during construction for this case. We typically analyze as a regular Strength III load however the wind pressures would be calculated with this document which as expected are lower than the Strength III speeds/pressures calculated with the 9th edition of the code. This is just the table of contents but may be helpful.

file:///C:/Users/BrianWatkins/Downloads/GSWLB-1_TableOfContents%20(2).pdf

^ Revised link to the TOC which can be accessed for free:
https://store.transportation.org/Item/PublicationD...