The product fee covers the legal/valuation etc. Conveyancing is still done, sometimes a proper valuation too.
It's still significant. Usually 1k?
It was 1k for me.
That's a lot when interest otherwise is 1-2 pounds a day.
I'm pretty sure your getting your wires crossed.
There's no need for all that on a simple remortgage without extra borrowing. Maybe a conveyancing cost if you don't agree with their standard book valuation.
And with extra borrowing then you just get reassessed by the bank with income proof.
No legal fees unless you move property.
I did my remortgage with nationwide with zero extra costs and no product fee at all.