TMZ Hip Hop caught up with Shyne amid his vigorous press run for his upcoming Hulu doc "The Honorable Shyne," and he thanked Flex for the free promotion -- despite everything he's saying has been lies!!!

Shyne tells us Flex's beef with those hip hop heavyweights throughout the years shows his true character.

To drive home his point, Shyne rapped Nas' 2002 track "Purple" lyrics from the classic compilation "The Lost Tapes" to our camerawoman ... "The whole city is mine, prettiest Don I don’t like the way P. Diddy did Shyne with different lawyers ... why it's mentioned in my rhymes? F*** it, just an intro."

Shyne's recent press run has outlined exactly how Nas framed it in the song and ironically, he'd too began to bad-mouth Flex.

Nas once accused the radio legend of playing favorites in his battle with Jay-Z, a union that didn't last long because Flex threatened to end Hov years later on air.

Flex's trauma from the East Coast-West Coast rap beef has also surfaced throughout the years ... by randomly dissing Tupac years after his death.

If you remember, this all started when Flex dropped a bomb on Hot 97 a few weeks back, rejecting Shyne's labeling himself the victim.

Diddy immediately got word to us through reps, slamming Shyne's multiple interviews that painted himself as "the fall guy" in their 1999 NYC club shooting trial.

Shyne wound up in prison for nearly 10 years, and Diddy resumed his eventual climb to success ... but the Belizean politician says the last laugh is all his.