He 100% changed his harsh vocal technique in the past few years. He basically had no technique until around 2018/2019, when all of a sudden he started doing the more guttural growls that come from the diaphragm rather than the throat. No idea whether he self-taught or had someone teach him, but no question it was a conscious decision. It's honestly amazing that he didn't seriously fuck his throat up before then - must be very lucky with genetics. Stanne's throat began failing around 2002, which is why his vocals are noticeably different from Character onwards. Even though I love Damage Done as an album, you can hear he's struggling vocally on there, and his live performances from that time are brutal - in a bad way. Speed changed his technique from Natural Born Chaos onwards as well, to a more controlled style.
No idea how Anders kept going for so long without adopting a technique. There's a 2002 show from Seoul which is just awful to listen to. He sounds like he's in pain and even clutching his throat area at points. It's uncomfortable to watch - and a shame because it's a very nice setlist otherwise. It's noticeable in the bootlegs from the 2002/2003 period that Anders is having problems. I have one from London 2002 where he's literally just yelling, presumably because he couldn't growl or scream at all. Sounds like shit. He had some weird renaissance with his throat where he was suddenly pretty consistent again live between 2004 - 2007ish, then back to sounding mostly like crap until the past few years.
I don't know if you've ever seen the ASOP studio sessions, but boy, that's an eye-opener from a vocal perspective. You hear Anders recording his lines and it's laughable. No technique, just this shitty yelling which literally anyone could do. Even the production and mixing couldn't mask it, as frankly his harsh vocals sound horrible on the album as well. SOAPF sounds better (to my ears, anyway) but I think whoever produced the vocals on that album just worked some serious magic blending his voice with the instruments, as when you separate the vocal and instrument stems you can hear there's little difference between ASOP and SOAPF in terms of Anders' actual technique.
I didn't get to see an IF show for the first time until 2005, so I missed out on those earlier pre-Reroute/STYE shows. Jealous you got to see Nevermore though - great band who I unfortunately never got to see live. I think at that point in time people were likely going crazy for the incredible guitar-work and melodies in IF songs rather than anything Anders was doing. In Flames' fusion of death metal and Iron Maiden was very unique at the time, whilst being quite widely accessible (vocals aside). I know when I first started listening to In Flames it was the melodies that hooked me - I didn't even like the vocals at first, I just adapted to them over time.
