Not quite. An SSD at 85% wearout will take longer to program and erase the blocks and it will require more refreshes (data retention suffers) so there will be

Not quite. An SSD at 85% wearout will take longer to program and erase the blocks and it will require more refreshes (data retention suffers) so there will be considerably more background operations. In fact SSD vendors do quite a bit to make the disk perform its best early on when they absolutely can and then start to break down further down the road after the benchmark is over. After all the users are mostly only testing it for a month or two and they never get to a real wearout condition during the test and then they buy in bulk and run it for a few years but by that time the SSD model is already outdated anyway (about 18 month cycle for SSD models).