In general "interesting" is something players might want to try themselfs while "hardcore" is commonly used when players do not believe the same something to be possible and thus they usually don't even try. Your reply suggests you changed your mind from "highly doubtful/pretty hardcore" to "interesting" during the past few weeks regarding potionless playing.
Sorry Dr.Disaster, but your grasp of the English language has failed you yet again.
Engaging or exciting and holding the attention or curiosity.
Very intense or extreme
(Those are definitions from http://dictionary.reference.com/
in case you want to check the source. I didn't include all the variants of the definition because the others didn't apply to the context in any way. One definition of Hardcore was a 'type of music' for example, obviously doesn't apply so not included. Feel free to check the reference though, none of the definitions support your stance.)
So as you can see, something can be 'Very intense or extreme' and also be 'Engaging or exciting and holding the attention or curiosity.' I never said anything about a run without potions to not be interesting. Also what one person finds interesting, another may not. What is interesting to any individual person is their personal opinion and tastes. Similarly, what is hardcore is a matter of personal opinion as well since different people find different levels of things to be intense or extreme. For example, I'm sure you feel that beating LoG 2 on easy mode isn't hard, but I've got some statistics that prove that wrong.
If you look at the global stats for Steam Achievements you'll see that only 14.6% of the people that have the game on Steam have beaten the Lindworm regardless of difficulty setting. Now you might go and say, 'Well that includes all the people that have the game but haven't played it.' That's true, so let's only count the 74% of people that have the game and have beaten the first boss, those people clearly have played the game and everyone that has beaten the Lindworm has to have beaten the first boss, so we end up with 19.7% of the players that have beaten the first boss have gone on to beat the Lindworm. That's about 1 in 5 people that have actually played the game regardless of difficulty setting have made it past the Lindworm. I don't know what you think about that, but I think that sounds pretty hard. Then you start throwing other things into the mix like 'no potions' or 'no food' and you're taking something that already is hard and making it even harder.
The point here is that I don't have to change my mind about something being hardcore in order for it to be interesting. There are plenty of ways to play the game that I find to be interesting ways to play it and some of those ways are more hardcore than others, and some of the things you may have thought were easy, are insanely difficult for others, but that doesn't mean that all of those players that found it that difficult didn't find it interesting.