this doesn't answer the question specifically, but this could have to do with the answer as to if orientation has anything to do with output.

"This slow warm-up behavior is NOT common to all fluorescent
lamps. It is caused by the mercury amalgam used to control
mercury vapor pressure is most modern CFLs. Most linear
fluorescent lamps do not use an amalgam and will start at
50% to 60% of full output and quickly rise to 100% of full
output.

Some CFL manufacturers do not use amalgams and others have a
dual amalgam system. Either will provide a faster warm-up
cycle.


Why is the amalgam needed in CFLs but not linear lamps?


Because no part of a CFL is naturally cool enough to provide
the proper mercury temperature. Early CFLs had extensions
on the end of the tubes opposite the base called "cold
fingers". These extensions ran cooler than the main tube
because they did not have the hot discharge inside them.
Lamps that used cold fingers to control mercury pressure had
quicker warm-up than lamps that use amalgams. However, the
temperature of the cold fingers was different for base-up
and base-down operation, leading to differences in stable
light output for those two orientations. Since CFLs were
rated in base-up orientation, the cold fingers were
optimized for base-up operation. That meant that the light
output was lower when these CFLs were operated base down.
The US Federal Trade Commission eventually said that
manufacturers had to list both numbers (base-up and
base-down), or only the lower number, but they could not
list only the higher number. The amalgam was introduced as
a way to have equal performance for base-up and base-down
orientation."

-shake