I think a better way to understand how the minor scale was used in Common Practice is to look at it like this:
There is but one minor scale.
It has two variable notes.
For example, in the key of A minor, the notes that are commonly used (and what we commonly arrange in an order we call a scale) are:
A B C D E F F# G G#
Note that scale degree 6 appears in a natural and raised version, and scale degree 7 appears similarly.
The 7th degree is usually raised for HARMONIC reasons - to make a non-dominant harmony into a dominant one.
The 6th degree is usually raised for MELODIC reasons - to avoid the awkward leap of an +2.
To help us memorize this, people came up with 3 scales - Natural, Harmonic, and Melodic minors.
But composers didn't "use a scale" to compose - they composed in a key and altered those notes for harmonic or melodic reasons.
For example, the i chord in minor is a i7 - A-C-E-G for example. You'd never raise the G in that harmonic context.
So the G (scale degree 7) is raised in chords that have Dominant function - V and viio.
In melodic contexts, typically, the "Melodic minor" scale is used - but again, rather than think of using a scale, I think it's more informative (and more like the actual music) to alter 6 and 7 based on their direction.
For example, the pattern 5-6-6 is going to use natural 6.
Likewise, 8-7- is going to use raised 7.
(unless a harmonic influence trumps those motions).
But, 5-6-7-8 is likely going to use both raised 6 and 7, and 8-7-6-5 is likely going to use natural 6 and 7.
Now, I say "likely" because there are always exceptions. You can find descending lines that are chromatic 8-7-b7-6-b6-5 etc.
If you know the Bach Bouree in E minor from the Lute Suite, it's a textbook example of how minor works:
E F# G F# E D# E F# B C# D# E D C B - it's got "harmonic" melodic" and "natural" element, but when you look at it, it's really about melodic direction and intervals.
HTH,
Steve