Or is it not the removal of foliage? I think you'll find it is.
Well, the way I do defoliate is to prune leaves - fan-leaves - away. When I lollipopp then I also take the shoots away - I rub the stems actually, to sort of tell the plant "do not grow new shoots here". I find both techniques have some similarities but also striking differences - so that's why we use different words, it's different.
Lollipopping is good for SCROGS - or densely filled canopies - where the stuff under the net won't get any light. So take it away, then the top buds will get better. And less hassle with popcorn or hash-making. Creates just more "for the bag".
Defoliation is tricky as there a several techniques which are basically the same - plucking off of leaves - just @ a different intensity.
Lowest would be 'selective pruning' - usually dysfunctional leaves.
Middle defoliation - which one should do in such a manner that still the canopy looks fully green as seen from above. This way, all direct light will hit a leaf right away - mitigating "reflection-loss".
Heavier form would be swazzing - where the latter point is ignored. This is done to increase the number of shoots, ultimately colas. Very suitable technique for commercial growers which need best 'bag appeal' - uniform smaller nugs.
Do you know that thick colas hold an enormous potential for the start of a pathogenic infection, like botrytis? Got hardly any airflow inside... beware of temp fluctuations when light goes off, just a good-ment word of advise.
To your second point, your bizarre example, it absolutely will result in a net loss of photosynthesis as a result of distance from light source to canopy, all things being equal.
In an open scenario - perhaps. But, in your situation - a closed tent with reflective walls - where shall the photons escape too? Light is energy and ther laws of physics state, this cannot be lost. The light just flies to another leaf - which absorb like 90% inside your growroom of the total radiant flux emitted.
There is a common mis-conception about the nature of light, when ppl claime it gets "weaker" by distance, and some therefore even try the point-blank range. And they falsely interpret the readings from their meters - which usually calculates for a m^2 - that is a plane.
With HPS you need distance as the source of light is singular, and thus, the light particles are together very densely distributed. But this distance doesn't incorporate any loss, as visible light particles can easily travel through our atmosphere and arrive equally at its target. To spread light out makes extremely sense, and is the reason why the current state-of-the-art lighting systems use a very high number of these cingular sources - to have the light be spread out *right from the start*. But no misunderstanding - the photon count stays the same. Light travels endlessly without a loss. The photons do not get lost - they just get distributed over a greater areal; which, in the above cases, is limited by the room.
My friend you are growing some heavy stuff - what is this for a strain/breeder? The plants have very little leaves so the light can reach down and you are growing thsee kind of "towers". Defoliation in your case is absolutely not necessary, but strains are different. Especially indica dom. strains can shadow their middle parts greatly.
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