I cannot confirm that this is true.
"Massive" entropy to me would equal the same strength as a randomly-generated private key. We must therefore first derive a random full-strength key and then discover a method of encoding that into "brain wallet words".
In my search for a libre standard-word dictionary, I found GNU Collaborative International Dictionary of English. From it, I extracted 131559 words, just a bit more than 2^17. At least half are not suitable, as they are multiple words or very obscure:
If we eliminate all but single words, the dictionary is ~2^16. If we give users the option of changing individual unmemorable words to at least three other words with the same identity, we are down to 2^14; 14 bits.
A Bitcoin private key is 256 bits in size. Therefore encoding 256 bits in 14 bit words = 19 words.
ECC key strength is commonly quoted as equivalent to half-length symmetric key algorithms. So, for example, a 256-bit ECC key would have roughly the same strength as a 128-bit symmetric key. However, the conjectured strength of secp256k1 may be as low as 50 bits in certain attacks. http://perso.univ-rennes1.fr/reynald.lercier/file/FLRV08.pdf. Therefore it is important that the first requirement of EC, full-strength random numbers for both key generation and signing, actually be used.
The reason Electrum words seeds appear shorter is they are half the length of a Bitcoin private key.
"constant forest adore false green weave stop guy fur freeze giggle clock" = 431a62f1c86555d3c45e5c4d9e10c8c7 = 128 bits
All Electrum addresses are deterministically based on something 340,282,366,920,938,463,463,374,607,431,768,211,456 times smaller than a Bitcoin address. Other Brainwallet schemes are even worse.
In conclusion, I'll just leave this here: https://bitcointalksearch.org/topic/ann-python-paper-wallet-generator-with-strong-randomness-361092