On a ticket it makes no difference on BA, unless of course you draw attention to it. Because legacy ticketing systems interface each other, some interfaces have been barely amended since the 1970s, so Mr Andrew Smith can easily end up as SMITH/MRAANDREWMR for example, if the ticket gets reissued. In some ways going back to SMITH/A (which is still allowed) would reduce this issue, but clearly a few reissues can still result in SMITH/AA. Every longserving ground agent at LHR will have their own example of hyper-mangled names.

Even on API, though I can only reiterate the advice to get that correct by the passport name, nevertheless the bulk of countries, including the USA, Canada and Australia, actually form the primary key off country code + passport number + date of birth. Some do country code + date of birth + pattern match on a numeric rendition on the name, since this gets around people swapping passports around, and it allows for some typo errors with names. Increasingly a second layer is being introduced where Large Language Machinery (or AI to use the incorrect term) is matching historic records based on the last line of the passport, or biometrics, with extremely high success rates, but that's usually for the benefit of border agents and their role in checking the checks.