You are going to be sacked. Give up your rights to an appeal and in exchange we will give you 6 months pay and agree a 'by mutual consent' statement. We have to have an answer to this by 18.00. If not we will put out a 'dismissed' statement. Until then the dismissal is pending.
(Just an example but from my experience this can take a few hours).
The only thing shocking about the club statement is the use of the ugly americanism "appeal the decsion". This is England and people appeal against things.
That apart, I suspect it was pending because he was offered another way out and rejected it (Disclaimer: This is a guess, I am not claiming any insider knowledge).
This is how I see it too - I'm sure it was abundantly clear on both sides that he was toast - just horse-trading to try and establish a clean break with no appeal (from the club's perspective); severance pay (from Gus's perspective) and damage limitation for both sides's reputation (agreeing wording of press releases etc).
Perhaps it would have been better to carry on the negotiation, but how long would that take? If Gus was so concerned about staying, you'd have thought that he'd cancel a media commitment to try to salvage his proper job with further talks? Gus's lawyers would know that the club need to put this to bed quickly to salvage some semblance of pre-season so would logically play for time to get a better deal.
I have no doubt that Gus is just playing to the media with the whole 'I only found out while working at the BBC' sob story - anyone who takes his statement at face value and feels sorry for him is at best naive, or perhaps just stupid.