Certainly a few Movistar riders did pause to get their rain gear on for the descent but Izaguirre obviously wasn't one of them because he was with Quintana on the descent.

I've been reviewing the recording I have of race and the Eurosport commentary and the first mention of the neutralisation was when Cataldo was 4km from the summit and they mention race radio as the source. The commentary team (inc. Sean Kelly) were very doubtful about how it was going to be implemented. As soon as Cataldo started the descent it was obvious he wasn't riding in a neutralised manner and was pushing on with the race car staying a couple of hundred metres ahead. By the lower slopes he was noticeably closer to the race car but still about 100m behind it.
Meanwhile, it was clear that Quintana and Rolland (each with one team mate) plus Hesjedal and one other rider from a minor Italian team had formed a chasing group. We were told that a Movistar PR guy had pointed out to media that the race organisers had deleted an earlier Tweet about the descent being neutralised. After some confusion about Uran's position relative to the chasing groups it became clear that Quintana's group was in fact the second chasing group and had a lead of about 50sec on the pink jersey and this stretched out around 1 minute by the 30km to go.

Prior to the start of stage 16 Quintana had been talking up Rolland as a rider he could form an alliance with and that's exactly how it turned out.

The race organisers seem to have had a case of the 'jitters' when they saw the actual conditions near the top of the Stelvio and probably regretted not cancelling it like last year, then started anticipating a disaster on the descent with lots of injuries and to cover their asses started talking about it being neutralised without really thinking through how this would be implemented.

What should have been done post-stage 16 to rectify the confusion? IMO nothing. Penalising Quintana and Rolland (not to mention Hesjedal)by a minute (the max. they gained on the descent) isn't really going to make up for the advantage they gained by getting away on their own and working together and it's wrong to penalise riders who are just doing their job within the rules and in the true spirit of competition.