That's the way a lot of us want it. But it has evolved a bit from its original regs. Initially you could only use "buckhorn" style open sights, flintlock ignition and patched round ball .44 cal or larger.
Today you can use FO sights or peep sight and any projectile (still .44 cal or larger).
If you want to use your in-line you can use it during the early ML season (anterless only) or during the regular firearms season.
If it were my choice I would have allowed the changes in sights but kept the projectile limited to the PRB.