I noticed the following situation. (AUR3 and 4 alike)

Weird summary.. so I hope a more telling explanation follows:

package x uses optionally package y but doesn't need it while building.

Looking at package x the optional package is displayed under Dependencies
Looking at package y I would assume package x would be displayed under "Required by" with (optional) behind it. But that's not the fact?


Examples
xdg-utiles-mimeo[0] and mimeo[1]. xdg-utils-mimeo lists mimeo under deps (optional), but mimeo doesn't offer the information at "Required by"
Whereas for repo-packages this is working.
julia[2] and gnuplot[3] for example. Julia optionally depends on gnuplot and gnuplot lists julia as an "optional required by"

_____
[0] https://aur4.archlinux.org/packages/xdg-utils-mimeo/
[1] https://aur4.archlinux.org/packages/mimeo/
[2] https://www.archlinux.org/packages/community/i686/julia/
[3] https://www.archlinux.org/packages/extra/i686/gnuplot/