You could very well be right and I have no reason to think otherwise! To be sure, you'd probably need to check with Spellings / Adrian Lees.
AFAIK MelIDI is the only MIDI Sequencer on RISC OS still actively developed and worth investing in. Anthem's hardware compatibility is adequate, provided you feed it with a Cakewalk .ins file or set-up an Instrument definition yourself. Alternatively, you can just assign each Song Track a MIDI channel and configure / program your synth to deal with it appropriately. Unfortunately there are some quite serious bugs and problems in the final version. Incidentally, there is also a Linux version of Anthem, at SourceForge if I remember correctly, though it's slightly different and IMO not as 'interface friendly' as the RISC OS version.