Water infiltration is measured by digging a small hole, filling it with water, and seeing how fast it drains. There's no way that regenerative agriculture has changed soil composition multiple feet down, which is what would be needed for the soil to absorb multiple feet of water.

I went to check the above sentence, and the first hit was this detailed article from Washington State, which analyses Brown's claims in detail, and explains why the scientific community is skeptical of them:

https://csanr.wsu.edu/regen-ag-solid-principles-extraordinar...

Anyway, even if, as Gabe Brown claims, regenerative agriculture is an order of magnitude more effective than expected, and you applied it to 100% of the land in Pakistan, it would still only reduce flooding by less than a foot.