I'll play devil's advocate, although your theory sounds logical.
McIntyre could have re-used a photo album, possibly one that had a lot of blank pages left, pasting over pics. I doubt anyone would have saved the negatives back then, much less gotten them redeveloped, but it's possible.
As far as the inscriptions, you could be right. It would help if we had a McIntyre signature to compare to. Inscribing 'Matty' as opposed to 'me', makes perfect sense if he's using the album to document trips that involved lots of people. I think I would do the same. Also, whoever did the inscriptions seemed to know all the same people that Matty would have known, frequently using nicknames. Using 'friend' in the 'Matty and friend' inscription makes less sense to me, unless the woman was someone who asked to pose with him.
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