I dunno 'bout that. A MWBC with reasonably balanced load running will have better voltage "control" as the voltage drop of the neutral will be canceled, thus halving the voltage drop each side's load experiences.
Regardless of the load type (early 1900s or early 2000s), the voltage control on the end of a MWBC is still good engineering to me. With respect to AFCIs, that may be changing. The new GE MOD 3 AFCI in the single pole 15 A and 20 A sizes can be used to protect a MWBC, as shown in a GE diagram that Dennis Alwon
posted here. Note that the MWBC neutral is only connected to one of the single pole AFCIs.
GE is, evidently, accomplishing this, in part or whole, by dropping the GFCI-like component of their breaker circuitry.
GE has released very little information about this development, even though the breakers are already out in distribution. I've even seen them on the shelves of the local Big Orange store just last week.