The NMLRA has been faced with stagnant membership numbers and in an effort to lure new members has moved toward greater acceptance of inlines. Even having matches for them. Most in-line shooters are not interested in competition and have an unfortunate false sense of superiority over traditional muzzle loaders if they could be lured out to a match. In line pistols have had a place in NMLRA matches for decades. but very few rifle matches were open to in-lines. The NMLRA's move has upset many of the long time faithful.
Frankly, a few states have altered their seasons to exclude/discourage in-lines from their primitive weapons seasons. Requiring loose powder, side locks, open sights, etc.
Pennsylvania's Game Commission kept changing the rules to permit non-tradtional muzzleloaders from nearly the very first flint lock season. Plastic stocks, day glo sights, short barreled carbines. pistol grips, etc. They did a way with the round ball requirement a long time ago. They are in part to blame for the in-line fans failure to comprehend the concept of a primitive season. If I had my way, the first week of archery would be limited to traditional wooden bows and arrows. No fibre glass, carbon fibres or sights until the second week. Training wheel bows would not be permitted until the third week.