pacman vs. Discover - again

[jojuma]

Hi,

some time ago I was told to run updates via pacman since Discover isn't trustworthy.
I am doing that for quite a time now.

But even if pacman tells me the system is up to date, Discover keeps informing me about available updates which becomes annoying...

My question is now:
Why is that? I'd think Discover is kind of based on pacman or from where does it retrieve its information?
Is Discover definitely wrong, when pacman claims the system is up to date? Should I run the updates via Discover or should I really permanently ignore it?

Thanks!