It seems like you can view it as one of two things:
- Bladesinger's don't have dailies. They have encounters that can only be used once per day.
- Bladesinger's have dailies that just happen to be encounter powers for a normal wizard.
Option 1 would poo-poo the tome trick, but open up Enlarge Spell.
Option 2 would poo-poo Enlarge Spell, but open up the tome trick.
Personally, I think the distinction of "Encounters as Dailies" exists solely to define which power list you pick from when adding spells to your spellbook under the normal methods. These spells are still dailies; they're just picked from the normal wizard encounter list. In every way they are treated like dailies, including them being unaffected by Enlarge Spell.
But, more importantly, D&D being the exception based game that it is, whether the items in the spell book are encounters AS dailies or dailies is irrelevant. The specific - the property of the tome - trumps the general - the bladesinger spellbook as normally presented - just as it trumps the general of the normal wizard spellbook by letting you have two more dailies than normal in it. Just like it would trump a Swordmage with a spellbook not normally having wizard dailies in his spellbook. Should you lose/sell/destroy the tome at any point, you lose those spells (since they're a property of the tome), reverting you back to the general.
Personally, it makes sense to me. A bladesinger can only perform a daily of a normal wizard's magnitude if they carry an uncommon magic item imbued with the knowledge of the spell. And it isn't terribly overpowered since you're still limited to 3 dailies a day and you're stuck with whatever dailies were in the tome at the time you obtained it, unless you want to spend a bunch of money to buy new ones. Arcane Power only has four such tomes in it; two that give you fire dailies, one that gives you cold dailies, and one that gives you summon dailies. Adventurer's Vault adds 2 more: one for lightning and one for force. So the really
good wizard dailies that enchantment/illusion Mages toss around stay out of your grasp.