Well, you could strip cambian layers out of those saplings the bear busted down pretty quick (a few hours would yield enough fiber strands to make that much rope), but you'd have to water cure it or something to get it in the proper condition. They certainly had the means, but you are right about the apparent timeline. Same with the hide, they could smoke cure it and break it easy enough, but the timing seems off. Books seem to do better at representing such sequencing, movies have limits on how they can portray such events, such as Redford's "Jeremiah Johnson" condensed event timing. Taking on a Griz or a Kodiak, or any other bear, with a few sticks does seem highly risky, but you make do with what you got, which is I think what the point was. They simply didn't have any options.

It seems to me, for continuity's sake, that they were eating the last of the bear meat when the coats were apparently done. That could indicate that considerable time had gone by (that would be a lotta bear to eat).

Yeah, it was a stretch at times. The important thing is it got those kids to thinking about it, and that was the whole point. Young minds properly harnessed can conceive of the impossible and make it reality.

Kodiak or Griz, either one will make a meal of you if you let 'em. You might chase off a black bear, but you ain't gonna scare off Ursus Horriblis or his cousin without Mr. Thundermaker or a big can of Eau de Peppy.