"While floating-point addition and multiplication are both commutative (a + b = b + a and a × b = b × a), they are not necessarily associative. That is, (a + b) + c is not necessarily equal to a + (b + c). ... "
"(2*pi*f0*t)" interpreted by MATLAB as ((2*pi)*f0)*t
"2*pi*(f0*t)" interpreted by MATLAB as (2*pi)*(f0*t)
As floating-point multiplication is NOT ASSOCIATIVE, both results might be different.