I think this entirely depends on the MIDI interface used. I have 3 different midi interfaces here, one is part of the maudio delta 1010 interface which is on the pci bus, another one is an maudio midisport 8x8 with USB, and a small 4 channel one “Midibox 4x4” also usb… The Midibox exhibits this behaviour, the driver gets locked and no other app can use the particular port which i tried to open in 2 apps at once. However the other 2 interfaces seem to be more transparent and their driver does not lock the midi device to the first app which opened it.
Im a hardware/software developer myself, and this issue is actually an annoyance cause a single solution might not work on any available midi interface hehe.