In both instances, you still need to bruteforce 12 words to get the actual seed phrase... So, you're working with a 2028^12 search space... which is 5444517870735015415413993718908291383296.
I don't think we can call it the same. If the total words are 12 and you are missing all 12 then the search space is 2
128. But if the total words are 24 and you have 12 then you still have half of the entropy and depending on which half it could be a lot simpler. For example if you have the second half of the words then the
bulk of the search space is suddenly reduced by roughly 94% because of the checksum.