Just who might you two have been thinking of
well I didn't want to say names

10 is like the Great Longneck Scheme as far as why it was done IMO...
Don't you think Grosvenor received numerous letters/emails/whatevers asking "what happened to Littlefoot's dad?" just as much as "when is Ali coming back?" breaking it down to basics gives you the reason for what might be considered poor effort
A refers to Ali, B refers to Bron
1{A & B}. Grosvenor just wanted to stop receiving emails/letters asking these questions, he'd heard it before, and probably got tired of it
2{B}. The story left no explanation as to what happened to his father other than his suggested death, and since it hadn't been mentioned ANYWHERE beforehand that his father was around, or ever existed it's kinda clean-slated, it had been far too long to make any story of him searching make sense to the over-analysts... *ahem* so he probably just did what he could...
2{A}. Grosvenor did NOT create this character, so what he did was went with some ideas he had based on what he saw...
she is fairly unquestioning: She wouldn't work with the others.
she is easily swayed: oh he's a longneck he must be alright: Littlefoot and Rhett
she's not the best decision maker: going alone to the land her mom didn't want her to go to, because she didn't like the others for no reason
she said herself she's been so many places she can't remember them all very well, it didn't say how long she was with or how attached she was to each place
Thusly, the character IS
fairly accurate to the original, and maybe she didn't seem too accepting of her old friends because it'd been so long she barely remembered them that much...
If you need to understand this further, what if I gave you a character, and an hours' info on something that happened to him/her, but not a TON of info about him/her? could you make a 100% accurate story about him/her?
3{B}. Bron may have been gone a while before he started looking for Littlefoot and his mom, in which case maybe he (too) forgot about the Great Valley, there's no strong noting of time
3{A} Grosvenor made this episode with no narratorial response stating she'd return from here, which would probably lower (tho not definitely) the amount of letters and whatnot he'd receive
4{B} He (or his staff) DID create this character, so he is at liberty to bring this character back, he KNOWS this character...