An official tweet from Niantic announced that inviting Friends to Raids won’t launch in June. The reasoning behind this decision are technical issues that keep popping up with releasing this feature.
The feature is designed to allow players to invite up to 5 friends to participate in a raid, regardless of their location. Here’s how it works:
It seems that developing the system raised a number of potential technical issues. In order for the system to work, Niantic has to be able to push notifications reliably and timely, as raids are timer based encounters. The frequency of these notifications is much higher than friendship invitations, which could be a potential bottleneck for the system.
Another potential issue could be player presence at different locations and how that plays along with Niantic’s shadowban and spoofing detection system.
Unfortunately, Niantic did not share which issues they are referring to, so this remains only at speculation level.