An equal sign may be used in several different senses, perhaps too many.
a) Describe an identity
b) Assign a value
c)Describe some equation (to be solved). (Ask not answer)
d) Describe some unobvious scientific result
e) More?
Now a=a is taken as a tautology. However a=b is not.
Why? Because in principle aand b could be different numbers, so a=b describes a coincidence,
perhaps a huge one. a=a just means a number equal to itself, no coincidence.
Now the question arises with (normally called identities)
xx-yy= (x+y)(x-y) that some would call tautologies. Are they really. ??
Math is so full of them , that some think math is all about them.
Or take cos(x) cos(x) + sin (x) sin (x) =1
Is this information, coincidence or tautology??
Are there accidental identities in mathematics, or are they all of a deterministic nature.(for a good reason)
For example in what category would you place the Fermat non identity with n> 3 or = 3??
Or the random distribution of the prime numbers??