If the MIDI file is format 0, does the JUCE MidiFile class break the events into different tracks based on the MIDI channel number of the event? If so, I agree that you don’t need to know whether you have a format 0 or format 1.
However, if it’s a format 0 file and the data is not split, then you definitely care whether it’s a format 0 or format 1 file because on a multi-track file, you often won’t care about the actual MIDI channel of an internal event and you’ll want to assign instruments based on the track number, not the MIDI channel number.