Why does paru have sequential download - build cycles instead of already downloading the next package in the background?

When running cachy-update, pacman first downloads all packages in parallel and then installs, aur downloads are handled by paru, which sequences as follows:
Download Package A and everything needed to build it
Build Package A
Download Package B and everything needed to build it
Build Package B

etc.

I can't remember if I'm also asked to confirm the changes each time before proceeding with the next package, I think for cachy-update I confirm once, but when installing new stuff, I have to confirm each.

I understand that conflicting dependencies may make this more complex, but why not let the user confirm for every package first and then already download the remaining packages while a previous one is being set up? Probably it's due to lack of technical understanding, but this seems unnecessarily slow.

https://redd.it/1tq1f4n
@r_linux