This is not a discretionary appeal of a lower court's decision, which a Supreme Court can either accept or reject. If you look at the caption, this is not an appeal of a lower court's order; it is an original writ petition. The Court has no discretion to not hear it; it could have either denied it -- which would be a denial on the merits, unlike a refusal to take the case, granted it without asking for a response, or asked for a response. Given the high profile of this case, it was "inevitable" that the Court would take the third option.
Every appeal to a supreme court is a petition. It doesn’t matter what the subject of the petition is, a supreme court always has discretion to not hear a case. You said so yourself but chimed in that it was “inevitable” it must be heard. Yherefore, you are confused.
The fact is the MS Supreme Court has decided to hear the case and that is a win for McDaniel.