is Python-syntax-in-CAS less accurate than PPL?

[parisse]

Nothing, tan or math.tan is the same. You don't need all the math import or math. stuff, they are just here to improve compatibility for people who would like to run existing Python scripts or are comfortable with Python and want to write Xcas programs.
Floating point numbers are CAS floats, i.e. 48 bits of mantissa instead of 53, therefore you will not have full accuracy but almost, like in CAS.