What is the problem?
If you use synth both ways, with and without external clock, any patch with seq or arp applied will not play if clock is set to ext but no external clock is recieved.
go through and quickly listen to presets then is a nightmare cause you have to manually deactivate seq and/or arp in every track in every preset.
What should this feature achieve?
A auto clock setting (fallback to internal clock, if no external clock is recieved) would be great to solve this hussle.
OR as alternative:
A global off setting for seq/arp would be really usefull and maybe easyer to implement.
both methods could save time, frustration and some false “bug reports”
Are there any workarounds?
Yes, you could switch to internal clock every time but if you forget about this, the trouble starts again, that means IF anyone thinks about this after a lot of frustration and cable checking 
Any links to related discussions?
.
Any references to other products?
Analog Four, Digitone/Digitone2, Digitakt/Digitakt2, Syntakt, Analog Rytm, some Korg stuff, a lot of multi fx boards, etc