Yep, I've heard this before.
It probably keeps you very regular.
It was also used as a topical antiseptic back in the day, although it has no anti bactierial qualities It will seal an abrasion pretty well.
The only thing that I use it for is the good old Petroleum Jelly Cotton Ball (PJCB) fire starters that I have in my fire kit.
Although they are kind of messy.
I've also found that a cheap crock pot from a thrift store will melt old candles and crayons. Tear small strips of newspaper, roll them up and tie them with some thin string, then use the string to dip into the crock pot and dry them on a piece of wax paper.
Less messy for just as good a fire starter.
The harder wax holds up better in warmer weather than the Vaseline.