Your Story, Page 20:
The entire Fate Points section from p19-20 appears to be talking about player capabilities, not character abilities. Note the first paragraph of the section on YS19 in particular:
"Fate points are central...they are basically a measure of how much power you have to influence the story in favor of your character." And the beginning of the second paragraph:
"Each player begins the first session of the game with a number of fate points..."Rereading the text you quoted with the section's context in mind, it seems apparent the player needs to know about aspects in order to use them, not the character.
Edit: Also, on page 105:
Yes, as you quoted, the character needs
"reasonable access" to the aspect...which is different from knowledge. Also part of your quote, simple presence in a scene is usually enough to use scene aspects. Presence, not knowledge.
Flip back to YS98 and the beginning of that section on aspects, it states:
"When you can apply an aspect to the situation your character is in, is can be used to give you a bonus." Again, it's the player applying the aspect and not the character.
Closing the book and going purely from a 'what makes sense' point of view, I'll still allow players to invoke things their character may not know about. Consider a situation where the characters are entering a fight with someone who already has "Broken Ribs" - I think that injury is potentially relevant whether or not the characters know it. It would certainly affect most fighters. The same applies with less obvious scene aspects or even city aspects, and why have city aspects if you'll never use them?