Yep,
Pretty sure my squirrels would slide down the fishing line, too. I have an expensive "squirrel proof" feeder that hangs from a large metal crook. They slide down the hanger (stainless wire) sit on the lid, then slide down the side of the feeder until they land on the ring that closes the ports so they can't get to the seeds. Each one of my many squirrels must have tried it a few times. Now they've discovered that instead of doing the slide, they can reach or jump up to the ring, open and close the ports a few times and send a little shower of seed down onto the catch net (an 18in. circle of window screen) under the feeder.
The birds spill a lot of seed, and I've just had to be satisfied to let the squirrels have what the birds spill without making them forage around on the ground and drive the cat crazy. So the catch net is now the squirrel feeder under the bird feeder.