That's a different problem altogether. Which you won't fix by bending over. Once Knots and better tools for decentralized block templates are the norm it will change.

Then why set the filter to 100k by default? Why filter at all? Why not permit up to 500MB or even no limit at all?

Because the block size. We don't want large blocks, that was a debate a long time ago, and we agreed that large blocks have more downsides than small blocks.