Thats how BIP9 works right now. Perhaps experience with the first BIP9 deployments (CSV/etc.) will cause the spec to be changed, but for now it's reasonable to assume that it won't be.

(There is a lot more to the trigger threshold than just "95%"-- BIP9 gets rid of the rolling measurement so the 95% from BIP9 is a much higher bar than the 95% from the rolling method used in the past; the network has never used a bar this high for a soft-fork deployment before, so we may learn some things during the roll of of the first features with it.)