By choosing this as a 'line' with no exceptions it creates a situation where a recreational diver going to 0.001 minutes NDL on their computer is perfectly acceptable but going 1 minute into decompression (and the few minutes that might add to the ascent) is completely verboten. This results in a lot of sheep standing 1" away from the electric fence at the edge of the field because that's where all the tasty grass is. That is - one has created a situation where a lot of people are operating to 100% of their limit even on a 'typical' dive (because they've been told it's a-ok) and have no idea what happens just beyond. What happens to the sheep that one day finds itself on the other side of the electric fence?
By deliberately pushing just a little bit into deco (in the context of a person's particular computer's assessment of the situation) and then safely making ones way back out now the '100% knowledge capacity' threshold is extended. Any dive undertaken within computer NDL limits now becomes a 90% knowledge capacity activity for that diver with a nice smooth grey transition area up to 100% - no longer a 'line'. I would suggest this probably makes each 'typical' dive now inherently safer but, more importantly, if the threshold (which is now at 90% of capacity) is violated by accident that diver is still operating within their knowledge and training. They know they shouldn't be there - but they've been there before and can safely get back.
Lines are only good for the types of people who colour within them.
I should definitely emphasize that my advocating this experimentation is 100% about 'learning you're computer' and not about 'learning deco procedures'. Doing it once - and only once - in friendly conditions (lots of gas, etc.) for a timespan only long enough to make the computer react is really not adding any risk (certainly less than doing it accidentally and unprepared at some point in the future). Ideally this would be integrated into an AOW type course to allow for supervision/guidance - but that might distract from PADI's latest course development efforts on how to best colour match your fins and weight pockets....
In the context of this thread, I disagree. The problem with pushing a limit is that it increases your decompression stress and risk of DCS, especially with multiple days of diving, even if the magic bracelet says that you are safe. That is the take home message, and it holds for air or nitrox, as mentioned upthread. It should be stressed that the NDL line is a bright line through a grey area - that is, a somewhat arbitrary approximation of safe N2 loading which will keep the vast majority of people from getting bent. But it's no guarantee.
On the other hand, to address the "sheep" issue, the way that you communicate to recreational divers about what lies beyond that line is to tell them that they shouldn't plan on doing it without training, and appropriate redundancy and gas reserves. But you should also tell them that if for whatever reason they find themselves with a deco obligation, just follow the computer and do the deco. You don't need to do "a little bit of deco" to make that point. By suggesting de minimis cases ("what about just ONE MINUTE of deco? Can I do that?"), we normalize variance and make the next person push it a little further.