When a name morphs as Percy's did from one form on the birth registration to another later in life and/or on the death registration, I look carefully at all the records for the person, plus all the records I have from the parents, sbilings, and children. From that comparison, I try to decide if the spelling on the birth record was a one time misspelling of the kind that these days I would consider a typo. If, and only if, the spelling on the birth record is a one time obvious error, I will correct the spelling from the birth record and use the corrected spelling as the LNAB.
On the other hand, if the spelling on the birth record is one of several spelling variations for the name, and was not a one time use, I use the spelling on the birth record as the LNAB and put all the other spellings in Other Last Name. This can lead to family members with different spellings for their LNAB, but as long as you put the other spellings in Other Last Name, any of the spellings will pull up the profile in a search.
Sometimes it is a case of the spelling morphing over a person's lifetime. In that case, there really is a difference in the LNAB and the Current Last Name (the one the person died with).
I don't see much point in having separate fields for Last Name at Birth, Current Last Name (or last name at death) and Other Last Names unless we use them to match what is on the birth and death records.
That still leaves a conundrum when there is both a baptismal/christening record and a civil registration record for the birth and these two use different spellings for the surname. Then I dig deeper for clues of what the family itself used. For example, if I have the actual baptismal record image, I look to see who signed and how the family itself signed the name. If there are no images and spellings are different, I tend to look at all the records I can find of the family at or near the time of a birth and see if one spelling predominates in that time period.
It can eventually get sort of subjective especially if you only have two records available and they differ.
No matter what the records say, I try to discuss all name variations and name spelling variations in the biography.