What were my complaints about mixing with them?
This, your first sentence of your first post I replied to:
I tried mixing with these for a long while, but the stereo width is so narrow that I consider them nearly mono.
You tried, for a long while, but they had shortcomings. That's a complaint, no?
I consider the stereo image too narrow because of a hyped center that masks the sides a bit, especially in comparison to the HD650 and Salnotes Zero which have essentially crystal clear sides with a more balanced center within the overall image.
The advantage to that is being able to balance energy in the sides of the mix with more confidence in comparison to references.
In regards to Scheps, he did mention quite a few times that these remind him of his old Tannoy speakers, and also said he didn't use any FR correction on them so I do believe it was both the frequency response and stereo image of these he was drawn to, even though he also basically made it seem that he only was using them because he had a lot of them laying around for drummers to use while he was acting in recording engineer roles when he was operating as a producer out of his studio.
But that's just me reading the tea leaves after trying these for a few years based on inspiration from his interviews.
I think these were a studio standard in the past mostly for monitoring for tracking, but IEMs would be far better suited for the task today, especially for minimizing headphone bleed into mics.
Sure, I'm not complaining that you have an opinion. I was just giving counterpoint, mainly to the idea that Scheps was perhaps not addressing certain details due to shortcomings of the headphones—I thought that might not be the case, due to his history before using headphone. It's just my thoughts, I'm not saying you're wrong and I'm right.
And you know I don't used them, though I did for years, as budget friendly headphones adequately suited for tracking and for scrutinizing tracks. I've used MDR-7520 for years as their replacement—not because they are the best overall sounding headphone I own, but for similar reasons to why 7506 is useful in recording (except a lot better, including a much better sense of warmth when performance a vocal take).
Sure, it seems a little weird that Scheps uses (or can use) 7506 for mixing. But not that weird, people mixing on all sorts of things. And often it's not the case that they get their mixes on large monitors, then only check and adjust on things like Auratones. Sometime they are mixed on tiny speakers, for tiny speakers. I remember a few tunes that I heard on a little boom box, and thought, "wow, huge sound—I bet this will sound awesome on my home speakers!", only to find it sounded tiny and tinny.
In fact, Scheps is certainly a bit that way, he likes his mixes to sound "loud", which is definitely at odds with "balanced". He says he annoys mastering engineers by delivering loud mixes instead of letting them deal with that. I remember Scheps saying that one of the satisfactions he gets is when he's out somewhere and someone is playing one of the songs he mixed on a mobile phone, and it sounds big.
For fun, a couple that come to mind—here's the one I recalled sounding so big when playing it on a small radio while doing some work, then being hugely disappointed at the sound on a good stereo...famous for being maybe the only song to rhyme "parthenogenesis":
Here's a more famous one that sounded so huge on tiny TV speakers, but is pretty hard on the ears otherwise. There's a heartwarming story of the guy who mixed and produced the album, so distraught over how it turned out that he called his mother crying and was going to join her in real estate business or something...then it blew up on MTV and changed his life:
