Firstly, debate is one thing but accusing people of guessing versus posting what they believe is right is a different story. I do not find that Bob or Dennis guess very much as most of their posts are based on the NEC and how it reads.
I personally ( maybe it is just me ) do not see where your examples of 240.92(B) or 240.21(B)(2) applies to any of the OP's question. We are not talking about taps in regards to the overcurrent protection at the tap location and so on that those reference you gave apply to. We are talking about the extending of an existing circuit.
250.140 Frames of Ranges and Clothes Dryers. Frames
of electric ranges, wall-mounted ovens, counter-mounted
cooking units, clothes dryers, and outlet or junction boxes
that are part of the circuit for these appliances shall be
connected to the equipment grounding conductor in the
manner specified by 250.134 or 250.138.
Exception: For existing branch-circuit installations only
where an equipment grounding conductor is not present in
the outlet or junction box, the frames of electric ranges,
wall-mounted ovens, counter-mounted cooking units,
clothes dryers, and outlet or junction boxes that are part of
the circuit for these appliances shall be permitted to be
connected to the grounded circuit conductor if all the following
conditions are met.
(1) The supply circuit is 120/240-volt, single-phase,
3-wire; or 208Y/120-volt derived from a 3-phase,
4-wire, wye-connected system.
(2) The grounded conductor is not smaller than 10 AWG
copper or 8 AWG aluminum.
(3) The grounded conductor is insulated, or the grounded
conductor is uninsulated and part of a Type SE serviceentrance
cable and the branch circuit originates at the
service equipment.
(4) Grounding contacts of receptacles furnished as part of
the equipment are bonded to the equipment.
If the ovens are being moved to a new location then it is not existing anymore and thats not guessing anymore than you are guessing that 240.21(B)(2) applies which is for tap rules on overcurrent protection afforded at the tap. In the end it will be up to the local AHJ to determine in their own mind what constitutes an existing branch circuit versus the line when it is no longer considered existing, in the end everyone is guessing based on what they consider existing and where they draw the line.
Point is, no one is guessing. They are posting on what they believe is right as you are also and I dont see anyone saying YOU are guessing?... I post here all the time certain things JUST to hear others chime in with their opinion and sometimes I agree and sometimes I dont.....it's all good but I would not say we are all guessing when it is what we believe is correct.