In my humble opinion it is not as simple as you are saying.
"Not modifying" still does not take away the copy left effect of the AGPL if it's a part of your program.
Hence the conveyed work (meaning your program) if linked with AGPL libraries still has to be available in a source code as a whole. Section 13 mentions that linking and in my perception relates to section 1 “Corresponding Source” (basically anything that is need for the program to run...).
Coming from that you really don't modify the original AGPL part but still you are obliged to reveal the source code of a whole combined work :)
All the above is required unless the original AGPL parts are aggregated (Section 5) or they are not a “Corresponding Source” as per Section 1.
I'm happy to discuss if you disagree the license is pretty complex...!
I wish the rest of the UE is included in the giveaway...
maybe next year? :)