No argument save that all of that shouldn't make you exemplary or unique in the way the rules present. It makes you motivated. Frankly even class levels shouldn't make you special because everyone should have them. (The NPC classes of 3.5 fell into this trap to for the Warrior and Adept, imo.)*

Johnny Haysee who had some training in the town guard only to lose his family when his village was murdered by a sudden zombie incursion, who then goes on a vengeance fueled life of adventure to gain the power to fight the necromancer that created them isn't any less of a Johnny Hayseed who signed up for basic training, washed out, and then decided to go adventuring. Either can fight but no better than any other guard at lvl 1, because all lvl 1 guards should be fighters (or some other class, not to go too deep down the rabbit hole of "what classes should have what skills in what jobs"). What makes the Adventurer special is their motivation, but their motivation shouldn't start them with super-powers. It should deliver those to them as they explore the world, themselves, and their abilities.

(*) I guess you could define class levels as adventurer only, but even then at lvl 1 I'm not sure you're "better" enough to qualify as meaningful, and in 5e at least its irrelevant because the divorced system between opponents - even npcs - and players means its all nonsensical to justify anyway because the town guard there isn't a Fighter lvl 5 by the rules its a Monster labeled Fighter and will be stated according to what would be a challenge for the DM's needs. Which demands a lot of world based hand waving but that's not what the conversation was on.