It was not generated using iancoleman tool. The maximum number of word it takes is 24 words, as you can see in the picture below
Possible, using custom entropy in the checkbox. The words will still be derived from the list.
@OP, the benefits of extra entropy diminishes with the increasing seed phrase length. 24 word seeds are already an overkill, 12 words is sufficient it provides for 128bits of entropy. It is far easier to have to type/store a 12 word seed than a 24 word seed and of course, 600 word seed. Most wallets do not support seed phrases that long and there is really no usecase for anything like that.