In removing the electrical double oven, I found the ground and neutral
from
the oven were connected together to the feeder neutral. The existing
feeder is 3 black wires (2 hot, 1 neutral) plus a bare ground. Does it
seem odd that the ground wire from this service was cut back at the
junction box and both appliance ground and neutral were tied to feeder
neutral? The main circuit breaker panel is grounded so there is no reason
not the use the feeder ground, right?

After you make sure it was wired correctly at the breaker box, there is no
reason not to use the ground. You are lucky the electrician anticipated the
new code. Mine is just 3wire.