During installation, using Expert Partitioner | Start with existing partitions:

When manual mountingpoint option "/boot/efi" 

Although not a bug, I also noticed here that an enhancement would be when
manually mounting an existing EFI Boot filesystem, if the installer automatic
filled in /boot/efi as the suggested mount point. 

That is, behave correspondingly and consistently as it does when mounting a
swap file system by automatic fill in "swap" as mount point suggestion. 

Typically when setting up a dualboot installation with Expert Partitioner and
Start with existing partitions, one just want to re-use the existing /boot/efi
and swap file systems. When finally also "Import existing mount points" is
re-implemented, this also come automatic here.