In the land of Hyrule, there
echoes a legend. A legend held
dearly by the Royal Family that
tells of a boy... A boy who
after battling evil and saving
Hyrule, crept away from that land
that had made him a legend... Done with the battles he once
waged across time, he embarked
on a journey.
Notice the difference between the MM quote and WW quote. Here there is no mention of Link fighting Ganon, but instead it talks about Evil. It talks about him essentially doing what he had to do and looking for a friend (who, given the fact this is said in MM BS, is Skull Kid IMHO). Link can be seen as a legend for what he did in the other timeline. Heck, he can be seen as a legend for being able to unite the pendants and use the MS. There is no contradiction here.
Uhmmm looking at the MM quote alone, we should know that the 'evil' is Ganon. I mean it's a sequal to OOT, it mentions time travel in that quote as well. You put 2 and 2 together--and you got the 'evil' as being Ganon from OOT. Hence:
'A boy who after battling evil and saving Hyrule, crept away from that land that had made him a legend...
Done with the battles he once waged across time, he embarked on a journey'.
A secret and
personal journey... A journey in search of a
beloved and invaluable friend... A friend with whom he parted
ways when he finally fulfilled his
heroic destiny and took his place
among legends...
Uhmmmm, who was the friend at the end of OOT that Link parted ways with...? The same person who we saw flying off after child Link placed the MS back in the Temple of Time--that's right, Navi. Skull Kid? I don't think so.
On the same pictures we also see the same looking Link fight Ganon. Are you suggesting that Child Link fought Ganon? Obviously not. The pictures don't work if you consider them to show Link as a child because he's shown fighting Ganon, and they don't work if you take them literally as an adult. Hence, the logical conclusion is to look at what we do know for sure. Adult Link fought Ganon and hence IMHO, the picture is of Adult Link. The fact it shows Link riding off just seems like what the people assumed what happened. Hence I maintain, there is no proof against a timeline split - only evidence for.
As suggested by the TWW intro and by the MM intro, the 'boy's tale' was a legend held 'dearly' by the Royal Family. When the story of Link's exploits across time gets passed along, people have there own vision of how Link and other characters in that alternate future might have looked. Keep in mind Zelda has been known to have clairvoyant and telepathic powers, so she could've seen in Links head what he might've been through. This story becomes dear to her and the Royal Family and it's passed along to the people of Hyrule from generation to generation.
Of course these people had there own idea of how this boy might have looked or how old he was (even Adult Link was a 'boy'--teenager to be exact). Maybe as the legends were past along, they didn't understand the concept of the way Link was able to travel through time. If I walked up to a person who never played OOT and say I'm a time traveller, they would think that I, the traveller, would look the same when I arrive in the future. (Just like the guy in Back to The Future looked the same when he time traveled--but of course us gamers know OOT works a little different) They wouldn't think I had to sleep for 7 yrs and my body had to grow, then I awakened, but when I travel back I'll revert back to a younger age. So as the legends were passed on the people assumed that he looked the same throughout his time travels.