Perhaps there may be a EFO (Errors, Varieities & Oddities) catalogue out there for these with their own number but I am not sure.
I enjoy seeing the misperf varieties myself.
The word Error used in
ebay listings (and others) may be there just to attract buyers.
The listing referenced may be priced a bit high but it is described and worded correctly enough. It could be only one stamp is wanted by collectors, or a lower price at this time, or the quantity of these is greater than the demand at this time.