I'd stop the work till this is rectified or explained to your satisfaction. In the past building codes usually didn't have a wind-loading rating required unless you lived in a hurricane-prone location. Your local codes may still not require that, in which case the window could be OK as long as you're happy with it. Just because the rating is lacking doesn't make it a bad thing- no old windows have those ratings but they work well enough. And the reason to stop the work is two-fold: First it gets the problem resolved ASAP and second it shows the contractor you will not accept questionable work which will hopefully get them to do a better job.
In my own business I resolve all problems immediately- that's the professional approach. I don't want my customers to have any worries or uncertainty about anything- I want them to know they're getting the best even when 'human' things happen. It can be embarrassing to me but I'll get over that; I won't get over having a call-back to set things right which weren't done right the first time around like they should have been!
Phil