My understanding is the P1 on a soil test reflects the available Phosphorus in the soil. It does not reflect total phosphorus in the soil.  So, if you had a P1 of 25, applied no phosphorus fertilizer, and had a P1 of 25 seven years later.... that says the available phosphorus in the soil is being cycles and replenished from the unavailable - or less available - phosphorus reserves in the soil.

You mention the P1 of 25, but you don't mention what the P2 number is/was.  You can have two different soil test results, both having a P1 of 25, and having very different P2 values.  

Rock phosphate vs commercial fertilizer.  To me, applying rock phosphate is no better than applying a multi-year rate of commercial fertilizer in one application.  In both cases, you risk having phosphorus being tied up, and then need to rely on the phosphorus cycling to become available.  I think you are better off applying annual applications of needed phosphorus, rather than "slug feeding" it.