Morgans writes:

The amount of time under chute is brief, and significant icing would not be
likely in that amount of time.

Sometimes icing can build up quickly, one reason why it is dangerous.
A parachute would not be immune to icing if the airframe was not,
although it might not build up as quickly (since the parachute is not
moving as quickly), and it might have less effect since the parachute
does not act as an airfoil. If it gets too heavy with ice, though, it
might stop doing its job.

--
Transpose mxsmanic and gmail to reach me by e-mail.