Basically, you shoot an ender arrow at the gateway and it will teleport you TO the gateway rather than through it, unlike the ender pearl.

Here's a video example: https://gfycat.com/FelineThinCaudata

IIRC there's a similar issue with EvilCraft's Blood Pearl. It might be an issue of "that's not really an Ender Pearl", with the EP's behavior special-cased.

Looks not that hard to implement. Just copy this into onImpact method of End Arrow

Yeah, I noticed that a few days ago and I have a branch set up with it copied over, I just haven't fully tested it yet to do a PR.