If the servo works, it is OK for the throttle. You don't need blazing speed or high torque. If it has balzing speed or high torque, it is a plus.

A little over a year back, I picked up a bunch of kits and "Stuff" from a guy who was retiring from the hobby. Included was a couple dozen S148 futaba servos and some mini servos. Not the micro ones use on the foamys, but about mid way between them and a standard servo. I used a couple of them for throttle servos. Works great. I use two for aileron servos,replacing an single standard servo. More than a enough torque, in fact I gained overall torque and cut the weight by going this way in addition to being able to set up flaperons.

If you need an extra servo, and one drops out of a tree into your lap and works, use it. The only caution would be to not pair it with another brand/capicaty servo for ailerons. About eveything else is fair game.

Don