Er, I dunno there's much to explain. Certainly the majority of my IR shots are with the sun mostly-behind the camera, my point was just that you can't really make a generalisation like "Do not bother to work with the subject back-lit by the Sun" because in some situations, it looks pretty cool. I find that most leaves have a good glow when backlit with IR, just like they do with visible-band. In some ways it's better than visual-band backlighting where you would generally get blown-out sky but with IR and blue sky, it's well-controlled as per my first post with the kiwi vines.
Same goes for side-lighting, it can give nice structural definition in the same way that it does with visible light. No drawbacks that I can see. If you don't like those photos or that style, that's cool, but it's probably my favourite way to shoot landscapes.
For non-translucent subjects (buildings, etc), sure, totally-backlit IR might be a bit crap.