No, it is not only about symbol politics.
The strategic location of Taiwan is too important for China to give it up. Taiwan forms the most critical link of the First island chain, a series of islands that could be used to keep the PLA Navy out of the Pacific ocean.
Additions:
- As @RonJohn commented: The barrier also works in the other direction, it would a be a great asset on preventing foreign navies from reaching the mainland.
- Controlling Taiwan would allow China to obstruct maritime traffic to Japan and South Korea, something unacceptable to them as both nations depend on access to foreign resources and markets.