A new date of September 11 was negotiated by Biden back in April...by July the situation had become more unstable, so indeed the longer time window was shortened by six weeks...
The Taliban has clearly not been sitting and watching...they took over every province w/o a shot...not anticipated...the Biden admin realized that they needed to move faster in order to secure a viable airfield (Kabul)...the new addition of 6K troops for that express purpose is en-route...Biden threatened 'serious consequences' for the Taliban if they interfere with the safe removal of American and Allied personnel...we'll see what happens, as the Taliban is an uncontrolled variable in this equation...just like in most war situations...things change and adjustments need to be made (i.e. 8/31 vs. 9/11)...but the strategy of negotiating more time for the removal of American and Allied personnel worked.
Am I wrong about my original post...i.e. Trump's actions on denying Special Visas seriously hurt our Afghan allies keeping them at risk of not being able to flee their homeland?...absolutely not.