... I haven't seen it for a couple of months, but as I remember the first part of reel 1 it was just them riding through fairly nondescript woodland and I don't recall there being anything on it which was particularly noteworthy, although I do recall there was a rock face which was fairly distinctive. But that may actually have been from any one of many of shots of men in hats on horses in S W Tasmania I've seen recently, I might just be getting confused.
Some sources explain the initial 70-some feet of footage on reel 1 by saying Patterson was collecting background or scene-setting footage intended to be used for either his already-in-progress (?) documentary project or perhaps a separate film focused on the recent (August) tracks find.
To the extent I've seen images from this earliest portion of reel 1, the foliage status (e.g., summer-ish versus autumn-ish) seems consistent with the sighting footage. My point is that if reel 1 was already in the camera, left over from some earlier filming, it's not obviously from back when summer was in effect.
There are two arguably minor items that bug me about Patterson shooting the environmental footage on Friday.
The first is wondering why Patterson waited 6 days (per the standard account) to get any such background footage. He could have been gathering it (and getting re-familiarized with working the camera) prior to the Friday sortie. The Friday sortie wasn't their first outing. I mention this because of the second bug-me issue ...
It was risky (or at least not especially bright ... ) for Patterson to head out on Friday carrying a loaded camera in case he encountered something significant, only to essentially squander 70% of the potentially critical film stock illustrating the woods.
On the other hand ... Nonchalantly shooting some background footage would have contributed to making the eventual reel 1 contents seem like a chance encounter - perhaps for the benefit of a Gimlin being groomed as a naive corroborating witness.
Another speculative angle would be that gathering the environmental footage was a goal - adding more of a realistic wrapper around an already-filmed encounter. A variant on this theme would be that new background footage was needed because extant footage obviously indicated a different locale or different time of year.
I would also point out that leaving only about a minute's worth of film afforded Patterson a ready excuse for breaking off an encounter that wasn't going as expected / desired.