I'm sorry, I'm not sure what you mean. In that paragraph of mine that you quoted I mentioned two issues and I don't quite know which one you refer to by saying "It" should only happen ....
Also, I'm not sure what selected list of glyphs you mean. I don't actually select any list.
I'll try to explain better what I mean.
1st problem - the misplaced diacritic marks: As soon as the base glyph's side bearings are being changed, the diacritics are no longer where they're supposed to be (and it doesn't matter if it's AutoMetrics that changes the base glyph's metrics or if I do it manually).
For instance, before running AutoMetrics my O's side bearings were 100 on both sides. Optical Metrics set them to 105 both. The problem is that AutoMetrics forces the LSB point to be at x=0. Thus only the RSB line moves and the O glyph gets centered between the bearing lines, while the diacritics in the O's composites stay where they are.
When I change the side bearings of the base glyph manually I can avoid this by simply unchecking box of the LSB point to be at x=0. Then both the LSB and RSB line move while the glyph itself remains in its position. But AutoMetrics activates that box automatically.
I don't know how the programming was different in FC 10, I just know that didn't happen. As PJMiller said, the relative position of the glyphs was kept, no matter how I changed the base glyph's side bearings.
2nd problem - the thing with the "Use this glyph's metrics" flag: I thought that, with this flag NOT set for any glyph member, the composite will have its own side bearings that I can change as I please, and so far it works. If I uncheck that flag for both glyph members, those little grey composite icons on top of the LSB and RSB lines disappear and I can now change the values (which I can't as long as the flag is set).
But I would also think that now changing the base glyph's metrics shouldn't affect the composite anymore. But it does.