Yeah if they're going bonded, it means he's on copper. I'd be interested to see what NID box is on the side of his house.
I'm the one who got 40/5 through bonded VDSL2 and it's been rock solid for me since install.
The speeds are generally as follows for 10+: 10/896k, 20/896k (for single pair ADSL2 service, or even VDSL2 sometimes as was my case)
I was able to talk them into installing 40/5 pair bonded after only being able to offer me either 20/896 on single VDSL2, or 20/2 or 40/5 on pair bonded VDSL2.
Try escalating to a manager, or have them transfer you to order support. those guys are good and know how to push just about anything through when necessary.. That guy i got there saved me from leaving CenturyLink after wanting to pull my hair out with normal tech support.