Das war mir so nicht bewusst. Die Vereinfachung einer potentiellen Attacke ja aber so drastisch!?
Da mache ich mich direkt auf die Suche nach dem vom Lakai01 angesprochenen Beitrag wo wir das bereits irgendwo stehen haben.

With good hardware, btcrecover will descramble a 12 word BIP39 seed phrase in an hour: https://btcrecover.readthedocs.io/en/latest/Usage_Examples/2020-05-02_Descrambling_a_12_word_seed/Example_Descrambling_a_12_word_seed/. Although not exactly the same due to the checksum, lets assume that if you know 12 out of the 24 words then you could descramble the remaining 12 words in roughly the same amount of time.

If you don't know the position of 13 words instead of 12, then there are 13x as many combinations to try, so that would take roughly 13 hours.
For 14 words, 7 days.
For 15 words, 16 weeks.
For 16 words, 5 years.
For 17 words, 85 years.
For 18 words, 1500 years.

No point calculating beyond that really.

In terms of an attacker trying to brute force a 12 word seed or a 24 word seed with 12 words known, jerry0 is correct though.

A 12 word Electrum seed with no known words has 132 bits of entropy needing brute forced.
A 24 word Ledger Nano seed with 12 words known has either 132 or 124 bits of entropy needing brute forced, depending on whether the checksum word is known or not.

There are other differences in regards to derivation path and so on, but broadly speaking, they are comparably difficult to brute force.