Yes, the MLB and nutrients are added to the must within 24 hours of adding the yeast. We understand that the environmental factors that affect the performance of the MLB are:
1. Available nutrients
2. Temperature
3. Sulfite levels
4. pH levels
5. Alcohol
With coinoculation, assuming that you've got your pH in range and add nutrients, you start the MLB off in an environment that is virtually free of sulfite and alcohol. As the alcohol levels increase, the MLB adapts slowly. Even with a sulfite producing yeast like BM 4x4, the MLB acclimates to that as well, plus, the increasing temperatures from fermentation are favorable to MLB. All of these factors allow the MLB to become well established and acclimated to the wine environment in which it can complete its work. MLF is normally finished very soon after AF and you can sulfite / protect your wine much sooner. Problems can occur if you don't properly feed both your MLB and yeast, as they can compete for food and produce some unwanted compounds. Feeding is important!!
Not a dig at sequential inoculation at all, but it can be more difficult for MLB to get established and functioning in an environment where the alcohol is 14%+, small amounts of sulfite have been produced or added, and temps are cooling down to the ambient room temps. Both methods are fine.