My view is that KV-62 was an unused and unfinished, and probably abandoned tomb, and there were minor voids that had been encountered, or natural cracks, a probably that apparently led to abandonment of other never-used KV tombs.
Tut died young and was given a hurried burial, and his grave goods (like those in KV-55, another burial from the last dregs of the 18th dynasty) were borrowed from others' former property. I don't think that was rare, it was probably normal practice, keepsakes and heirlooms from ancestors and whatnot were probably interred with pharaohs, we just don't have much to go on, since all the other pharaonic burials were plundered in antiquity.
The small size of KV-62 may have been a benefit given the short time frame available for the various rites and so on, and the unfinished passages and/or voids were walled off and/or plastered over.
[snip] Some have theorized that when Tutankhamen died suddenly at an early age, a tomb that was originally planned for him in the West Valley (KV 23 or KV 25) was not ready. It may have been decided to bury Tutankhamen in the main Valley in a tomb originally intended for Ay when he was still a God's Father, near the Amarna cache (KV 55). According to this theory, Ay later took the West Valley tomb (KV 23) after succeeding Tutankhamen to the throne. [/snip]Tutankhamen | Theban Mapping Project
KV-55 shown in the TMP’s pdf plan of the enormous KV-5.
https://thebanmappingproject.com/sites/default/files/plans/KV05_0.pdf
I haven’t heard that theory before, but it certainly could be the case.
(I’m hoping that there are more surprises behind that wall, however🙂)