If you are doing hidden tang octagonal wa-handles you can use a router sled with a jig to turn a rectangle into an octagon faster and more accurately than most grinding methods. Especially if you are doing large batches. A table saw also works, but a router could start the softening with the right tooling. I've seen this in use at Blenheim forge in the past.
Some of the concerns on using a router are due to the differences in knife handle materials. Lots of handles use burls and irregular grains that might tear out more easily during a cutting operation. If the handle isn't pure wood I wouldn't know what to be worried about; resin, copper, micarta, g10... each would have it's own concerns for tooling, safety, and finish. Most makers will use a grinder for versatility, unless they have a CNC mill that they use for semi-production (See Aaron Gough for an example).