If one types 1ciyam:2adfe rather than 1ciyam:2adfd then presumably you could end up with an incorrect address.
If all or part of the checksum was included then 1ciyam:2adfdeJu would be "invalid" (unless it was actually the same address).
That will hold if we include checksum of MinAddress itself rather than checksum of Full Address, otherwise we are just adding extra characters which needs to be compared, so adding the extra characters from the beginning is same as adding extra characters form the end.