Unless I'm misunderstanding, this is similar to what is currently recommended for storing passwords. Don't store the plaintext, store a hash instead (everyone's hash is salted, using a secure algorithm, right?), perform the same calculation on the input and compare (everyone's doing constant time comparisons, right?).
The problem is, someone out there isn't doing at least one of the above suggestions (or others that I've forgotten), or someone will intercept the original input while it's in flight (no one uses unencrypted connections on open public wifi, right?) or make use of some other arbitrary way that passwords can currently get stolen. And once they get that original digital representation of your typing style, you're done. That method will never be secure for you again for any service, unless you spend the time to change your typing style (and remember your new style should not be at all predictable to someone who knows your old style).