Here @ this site I have 238 pages of PMs now, going back as far as 2011
I think the reason why they say PMs can't be undeleted is two-fold:
1. Perhaps if the last recipient, as well as the sender, deletes the PM it does fully erase the text
2. The metadata is still permanently erased
vB PMs split themselves into two distinct parts;
pmtext
and
pm
. When you send a PM to multiple recipients, each of them gets their own entry in the
pm
table, but collectively only one entry in the
pmtext
table. Therefore, if one person deletes their PM, it's only the
pm
reference point pointing to the pmtext entry that gets erased.
Hopefully that makes a bit more sense