I wouldn't know for sure because I haven't done the factory reset. My understanding from folks above is that they didn't. some people I think reported that when they pulled from Verizon cloud the messages were actually there and thus they had them... they even got to see messages that they didn't see previous to FR because they thought the messages were actually in their phone (just not presented to them by the Android messages app) and then save to Verizon cloud when they did a backup and it wasn't until they did the factory reset and restored from Verizon cloud that they got to see those messages. Again though at least one person in this thread reported that the problem came back after the factory reset.
I was just offered an Android 8.0 security patch update by my phone, which I did... just letting folks know that that didn't fix the problem, I didn't expect it to really but I had a faint amount of Hope.
BTW, found a Reddit post where many are having the issue...
https://www.reddit.com/r/GooglePixel...m=comment_list