Its estimates are close at best to its intended target block (Within 1 block, 2 blocks, etc...), one block is an average of 10 minutes of waiting.
You can also switch to "mempool" slider for better control since you can specifically target to position your transaction within the maximum block size, but it depends on the timing.
You can set it to "1mb from tip" or lower 'mb from tip' and it'll be in a good spot;
But as I've said, if you timed it bad when a lot of transactions are broadcasted right after it, more high-feerate transactions could boot it out of that "1m from tip" position.
The catch is, it's not possible to compute the "correct" fee rate because mempools and mining are unpredictable.
So it's up to you if you want to pay more or less than the suggested fee rate.
The developers didn't changed it after SegWit update because they believe that changing that will confuse the users,
here's the reference: https://github.com/spesmilo/electrum/issues/6961#issuecomment-765541935