https://login.blockchain.com/#/recover work for 12 words standard phrases
https://login.blockchain.com/wallet/recover-wallet work for STANDARD legacy wallet recovery phrases (although they are longer but need be standard)
my mnemonic is from before this implementation - at that time the mnemonic = long passphrase was used by blockchain only to decode/decrypt wallet id and password - has NOTHING to do with the private keys
blockchain.info leave us alone, no help, no support for his OLD SHIT ...
The problem is that this mnemonic (passphrase) are not standard like 12 or 24 words seed + the words are not from the standard words list.
My mnemonic (passphrase) have different lengt, like 14, 17, 19 words
As you say, these are not BIP39 seed phrases but rather sound like the old style blockchain.info specific recovery phrases.
Have you tried inputting them to their old wallet recovery tool? Link here:
https://login.blockchain.com/wallet/recover-wallet