See this
answer where only one word is missing and we have so many possibilities so you are wrong on this part I would say.
There are not many possibilities if there's only 1 word missing. Considering the checksum, with only one word missing, there are only 8 possibilities on average.
Even if we don't consider the checksum, there are only 2048 possibilities and the seed phrase would be brute-forced in a very very short time.