What is the "heat-water-inside" boiler mode?

[AngeloidBeta]

The documentation for the BoilerPrototype says that the mode setting can be either "output-to-separate-pipe" or "heat-water-inside", and cites the latter as the default. However, I can't find a single shred of information about how this mode actually works, and experimentation has proven useless. Can anyone explain what this does?

[mrudat]

Boilers used to heat water in-line, but they were changed to create steam from water instead; I'm fairly certain the ability to heat water inside the boiler was actually removed? I might be wrong, though; apparently there's a mod that's replaced water+steam with H2O.