The previous posts are accurate but it can be the subtleties that get
you. The more general answer is "it depends".

Records and badges both use the same set of rules.

One of the "gotcha" items is, for example, your Diamond GOAL (the
300KM) flight. The 300KM must be (essentially) a "closed course" (out
& return or triangle) But the Diamond DISTANCE flight does not carry
that restriction.

You can, however, achieve a Diamond GOAL and Diamond DISTANCE in a
single flight that is NOT a 500KM triangle! In your example, fly your
300KM triangle then another 200KM to your endpoint. I you prefer to
keep our friends by not having them drive 200KM to retrieve you, you
could fly 100KM to your first TP, then your 300KM triangle, then 100KM
home to achieve the same (In SC terms: A Start Point, (3) TP's, and a
End Point).

Remember, "triangle" is loosely used here. It is really up to (3)
TP's. The "true" FIA triangle only applies to a category or record
flights.

Too confusing? The just fly "Free Distance" flights. But
unfortunately, Free Distance only counts in OLC and record flights.
There are no Free Distance legs in the Badge flights (well, except the
Silver dist, but why land after 50KM on a perfectly good soaring day!)

If you happen to live an an area that is not as geographically or
soaringly challenged as I do, you can fly your 1000KM and never be
more than 170 KM from home. Loosely defined by: Fly north 170KM, then
south 340 KM (passing your Start Point in the middle), then back north
340 KM, then 170 KM south to your start point.