That’s every bit as absurd as saying that a Dreadnought in DADGAD tuning isn’t really a guitar, and that the Spanish style, gut string instrument is the only true guitar. In fact, Manuel Nunes, the Portuguese luthier that came from Madeira to Hawaii and helped combine the Macheté and the Rajāo to create the Ukulele, and his sons introduced the first concert scale ukulele and the 8 string version.
Furthermore, there is extraordinary precedent across the rich landscape of music of instruments having multiple versions for various scales. To suggest that the same is not true of the Ukulele is to say that it’s not a serious instrument, that it is nothing more than a novelty item. So, unless you can present some historical record of the inventors of the Ukulele declaring that the re-entrant gCEA tuned soprano scale instrument was intended to be the one and only Ukulele, there is no convincing logical argument to be made to support your opinion as anything approaching fact. (You can, of course, state your opinion as to your personal preference in the matter, but you have zero authority to tell someone else that their Ukulele is not a true Ukulele just because it’s scale length doesn’t happen to be your cup of tea.)
Scooter