honda recommends AGAINST it at 1000kms
Fair enough, but any reason WHY? .. for interest sake.

Just because a manufacturer recommends against it, doesn't mean that's good advice per se. Personally, I'd want some reasons for the advice.

As an example, if you buy a new Falcon, Ford will recommend you don't need to change the transmission fluid on their 4sp auto for 100,000km. Reason - it will go that far without changing. My problem with this is that , yes it will go that far without changing, (just out of the warranty period), and then the whole auto will crap itself.
The better advice from auto-shops, is change transmission oil every 40k.

So what's the reason behind it from Honda?