After the race, they asked James Allison about that and he basically said that normally, as the race progresses they reduce the fuel mixture to reduce power output with an eye to saving the engine. At Spa, obviously near the end Raikkonen came under increasing pressure from Hulkenberg and so the team asked him to pick up the pace to make sure of 3d and the radio messages you referred to took place. If I remember correctly, Kimi responds with “So give me full power! Give me full power!”.
I may be reading too much into this, but I think Raikkonen was a little bit frustrated at that point. He’d obviously had a far from easy race in a car that wasn’t really handling as well as expected and desired and it wasn’t the first time in the race that the team asked him to pick up the pace either.
If you follow this link, at around the 4 minute mark, they ask him to pick up the pace a bit as well, earlier on in the race and he responds saying (I think) “Yeah, but I don’t have any grip, so…” with Simon Renni responding “Ok Kimi, understood. We need to push, push in harder and we’ll get the front tyres working”. Obviously that’s not how it worked out and after the race Raikkonen said they added a bit more front wing and lost even more top speed as a result.