That's simply not true. Windows update, on fully-functional modern hardware (Haswell Celeron with 16GB RAM), with an internet connection of at least 50Mbit/sec, using a DVD burned and verified OK, from an ISO of Win7 HP 64-bit SP1-U, downloaded from Digital River (before they were pulled), still takes OVER TWO HOURS, during the first Windows Update session, before it presents the list of updates available. This is fact.
My Skylake G4400 (stock clock 3.3Ghz, overclocked to 4.455Ghz effortless, verified stable by BOINC/DC projects), with 8GB of DDR4-2520 (OCed DDR4-2400), with a PCI-E 3.0 x4 AHCI M.2 128GB SSD, took slightly less time. Maybe over an hour.
Edit: Oh, and one core is pinned 100% pretty much the whole time WU is searching for Updates. The OCed G4400 having much better ST performance (nearly double the Haswell Celeron in the example), explains why it took half the time.
Edit: That red Brix mini-PC with the AMD Richland mobile quad-core CPU took nearly three hours. When you consider that the ST performance of a 2-ish Ghz Richland is probably half to 3/4 that of a Haswell Celeron, then it all starts to make sense. It's simply the sheer amount of processing that WU does, initially. It may be hashing all of the files on the HDD/SSD, before it sends them to the remote server to get the list of applicable updates.