It has never had a pro-PRC stance. That's a gross misrepresentation of the KMT view. At best, the KMT is a pro-status-quo party that simply thinks it's bad for business to start WW3 over the Chine issue.
There is no pro-PRC stance in Taiwan.
In fact Taiwan is split from the mainland because of the civil war between the KMT and the communists...
Parties do change over time. The Republican party used to to help black people...