I am sorry to say that the damage to the joists could have severely weakened them.
All manufacturers of this type of joist forbid any removal, notching or drilling to the top or bottom timbers as these provide the integrity of the design. Only the web (vertical middle area) can be drilled or cut and then only within strict guidelines.
You can check this on the Steico pdf here:
STEICO Joist guide pdfAny repairs must be done after the manufacturer has inspected the damage and any repair must be to manufacturer's recommendations.
All carpenters and site managers would know this! My advice now would be to immediately e mail these pictures of the damage to both the NHBC and whoever you are dealing with at Redrow homes.
In my opinion, some if not all of the affected joists may need to be replaced and by carrying on with the work they will only make a bad situation even worse.
You may like to send the pictures to Steico and ask their opinion as well!
The NHBC are providing a structural warranty for ten years and this damage is likely to result in a claim under the warranty, so I expect they will be eager to ensure Redrow do a proper job this time and not 'bodge' an unauthorised repair as the carpenters suggested to you!
By removing old floor boards that had been glued to the top of the joist, the damage was foreseeable.