All you're doing is using the same 23 words each time, and then finding an 8-bit checksum to match.

(Each word is actually 11 bits of entropy, so the last word is 3 bits of entropy plus an 8-bit checksum on all the random bits. You could either determine those 3 random bits in advance and narrow the list to the 256 words that match those 3 bits, or just pick 23 words and randomly pick from the full list for the last word until one works; this is a bit simpler but risks having to try even more than 256 words.)