I would hope they did cover the extra days.
The down side is you take out cover for a specific type of policy, not open ended, and so I would say its at the discretion of the company.
On a different scale, but still within the bounds of making an insurance claim, If I leave my car in to be repaired under an insurance claim, and my policy give me 5 days car replacement, but during the repair complications arise due to extra damage, non availability of parts etc, I still only get 5 days car replacement cover..but, most insurance companies would allow extra days grace when asked.
In your case, if the procedure costs more due to complications, I would have to assume this is covered, with the possibility of expecting a higher excess payment on your end
This is just a Laya persons opinion.