I guess I should add that I've been flying approaches behind a 530 (not 530W) for 13 years. I don't claim to understand every wrinkle of the box, I doubt that anyone does, but I certainly know how it works for approaches.
There has to be more to it than in the report. If you set up an ILS but forget to switch from GPS mode, you won't get a glideslope needle. That in itself should be enough to wake you up. Why would be you be descending on the glideslope if you don't have one?
I doubt that there's a 530 user around who hasn't at some time tried to fly an ILS with the box still in GPS mode, but after a couple of times you kind of wake up to the risk. And, as I said, there is no glideslope indication if you do that.
To expand on #1... it does bring up the ILS frequency as the standby, but it doesn't actually switch to it. You have to do that yourself.