[TR] What does the 70-71 TR6 breather assembly do?

[Lee Janssen]

I was looking at a TR6 1970 - 1971 Part 146725 'breather assembly' and
wonder what does this do and why did it disappear from all later versions
of the car?
On plate BF of TRF spare parts catalog volume 1 it clearly shows that the
outlet is lower than the inlet which makes no sense to me. I looked in the
Bentley repair manual (briefly) but didn't see a reference to the unit.
Thanks for setting me straight.
Lee