A4T vs Target reporting

[adityat]

I'm running 2 identical AB tests on a website homepage (1 with target reporting and the other one with a4t ) for all visitors.
Looking at the data I see unique visitors reported by A4T 40-50% lesser than those reported in target.
Visitor stitching looks fine all libraries are updated and loading in correct sequence.
Any thoughts on what could be the issue here.
Website has cookie bot enabled which is blocking only analytics call until accepted by visitor, target loads every time.

Additionally I've noticed A4T shows unique visitors as metric whereas target shows visitors. What is the difference between these 2.

Thanks.

Aditya