DerbyDad03 wrote:

But that's my point. "Hopefully" seems like a risky thing to base the
wiring on. It was obvious that prior work was not compliant, so why
would the electrician simply assume that the correct wire sizes were
used?

I'd be concerned with the possibilty that, let's say, 12g was used at
the panel but is connected to 14g in a nearby junction box or
something like that.

If it was a neat installation I'd have more confidence, but this panel
was such a mess, with obvious violations, that I'd have to suspect
violations outside the box.

I guess my main concern was the broadcasting of the practice as if the
wire size is all you ever have to be concerned with. It just struck me
as a dangerous assumption, especially in the sloppy conditions in
which the assumption was made.

What alternative makes more sense than the voice of experience that's
probably older than the funky wiring?
* Assume the possibility that somewhere there might be a junction box with a
bell wire connection, therefore every breaker should be 5 amps?
* Find, and inspect, every junction box, outlet, and switch to determine
wire sizes and hope there's not a hidden junction box behind a plaster wall?

You're right, it is a dangerous assumption. But it's also a trade-off.

Plus, the TV show you saw may have simply been using poetic license.