It seems to me that a no fuel condition wouldn't have anything to do
with the spark. To me, ignition means spark. If three cylinders were
dead because of lack of fuel, there still should be a spark?

If the plug gap was bridged, then the timing-lite pulse may be
deceiving. I believe there would still be a timing pulse even though
the cylinder wouldn't ignite.

I used a cheap inductive spark tester not a timing lite, on a DIS
system once, the lite was so irregular, I guess because of the exhaust
spark, I didn't like it at all, took it back and got the old regular
spark tester, where you could see the spark itself. I've never used
that on DIS ignition.

If you used a regular spark tester, the kind where you unplug the boot
and put it on the tester, on a DIS ignition system, would the companion
plug still fire? I'm going to try it one day, just out of curiousity.
It is interesting.