Welcome to Android Central! Since that Reddit thread is fairly long, I copied and pasted what I think is the most relevant post:
'Had this happen to me today, and figured out l about whole "GooglePlusBot".Steps to recreate this issue is as follows:
Use Google Messages for SMS on you phone with link previews enabled in app settings (this is default)
Try to restore your password on Instagram via phone
Google Message will try to fetch preview for link in the SMS
There you go - login from GooglePlusBot
So in case of "GooglePlusBot" there is no security risk. This "attack" is basically someone (or even you) just randomly tries to restore your account password and Google Messages follows link to build a preview. You can avoid emails by disabling link preview in Google Messages' settings. You will still receive SMS when someone's try to recover your password though.'