Fair enough! It is not completely unheard of for tamas to skip stages. There have been others who've said they've experienced the same thing. I cannot say it has happened to me. I know occasionally things don't work right with pausing and time alterations so the tama doesn't actually show the correct age - which may have occurred for you. Otherwise, don't be too concerned. You've got a masktchi - have fun!
The same thing happened to me. My Tamagotchi was a baby at 0, then a child at 0, then a Tennegaer at 1, then a Tarakotchi at 2. It's not a glitch, it's normal. Anything can happen to your Tamagotchi. In 2005, my Tamagotchi V1 was 3 and it turned into a Kuchipatchi (one of my favorites!). Like I said; anything can happen.