Good question, because I was looking at the form the other day in anticipation of advising someone in a similar situation, and I read it the same way.
The FLR form is for use for someone to apply as a spouse, but I think it was envisaged only for people applying for the first time, i.e. perhaps people who came here on a fiance visa. Somebody wanting to apply as an unmarried partner would have to show 2 years of living together, thus Note 5 under Section 8c is specific to them.
But you can't use the SET form for ILR, so it has to be this one. I don't think that they thought about what would happen to people who hadn't taken/passed the Life in the UK test, so they haven't made the form clear.
If you look at the ILR form, Section 9 presumably applies to all applicants, whether spouses or civil/unmarried partners, but the notes refer only to "you and your partner". So that's badly worded too.
Logic suggests that with your FLR application you submit as many documents as you can, if 4 x 5 as specified, all well and good, if not, you have a sound argument against them if they want to make an issue of it.
Thanks for that, well worth knowing
Thanks Keef and Lee