You have a point, as they meant to rename the players in a way that they could still be linked to the original ones (for example Figo > Ferreira or Totti > Tantalo). But most of them are credible even if "decoupled" from the player they are representing (I don't know if I managed to be clear). That's what I like of many of them.
For example, when it comes to Italy... Marchetti, Falchi, Tedeschi, Tarquini, Piacentini are all surnames that make perfect sense in Italian and that can live without the players they've been assigned to.
For each of those surnames I know at least a person bearing it, and there are also famous people with those surnames like
Federico Marchetti,
Anna Falchi,
Corrado Tedeschi,
Gabriele Tarquini,
Marcello Piacentini. Even if SEGA intended them to be fake, I think they make perfect surnames for "fantasy" players which have no connection with real world players.
The same applies to many surnames in FIFA International Soccer and in ISS Deluxe (I mean, I know more than one 'Pagani', more than one 'Mancini', a couple of pepole named 'Zappa' and more than one 'Premoli' myself).
You cannot do this kind of thing with names like 'Belbiero' (Del Piero's ISS 98 version) for example. That is a fake name that can't be used for anything else than representing the player it's intended to represent.
I mean, I get their point. They tried to make up something "sounding similar" to the real name, and even if for us Italians it doesn't make sense, it probably makes for them because it sounds "Italian-ish".
For example, for Del Piero I'd have used 'De Paoli' which gives the idea enough, and is a real Italian surname.
Them using "phonetically similar" names is like me using, say, 'Krankenwagen' as a fake name for Beckenbauer.
It sounds similar enough for me not speaking German to be credible and attributable, but then someone from Germany would certainly say
"did you really mean to call him an ambulance? Seriously?"
Ironically enough, my first username here was
'Kleimann' which is a name that for me,
despite being listed on Forebears as existing, is from the second category (can't be used for anything else than representing a player).