During testing I noticed that my upload speed was only about 10% what it should be

All the call handlers do is follow a script and very few have any technical knowledge at all. Once something does not fit the script the handlers seem to ad lib and often, from what I’ve seen on the board, give totally rubbish information to users. As you rightly say Cat6a is totally ok for 10G up to 30m and people are just wasting money using Cat8 cable in a home. There are some very knowledgeable users on the board who try to help users. Glad you got your connection sorted.