Yup, the extra shutter speeds are now there and working as they should.
Thank you so much!
The remaining problem is that the AutoISO in HQ mode doesn't increase to the correct level, at the expense of underexposing the picture. It only does that correctly in P mode. I guess, though, that to make it work well in HQ mode is probably a non-trivial issue, that will take some time to fix.
Either way, the enlargement of the exposure speed range is handy enough on its own. Thank you very much philmoz and waterwingz.