Its ironic as Lewis alluded. You cant pass the test for a lower interest rate so they whack you onto the usually higher SVR rate.
That makes sense no? The higher the risk to the bank, the higher the interest rate to try and hedge against that. Thats the reason you get better rates on lower LTVs; they are taking less risk of something catastrophic putting the risk bank on the bank if you default. Its the way credit cards work as well.

I don't know why you keep telling me about the 90 day window with current lender. I'm suggesting he talk to a broker and lock in a rate now with a different lender, up to 6 months before his fixed rate with current lender expires.