Yep, should just point out that it is equally valid to use both enharmonic equivalents (ie A# or Bb) when there is no scale context to define the note names. So if you’re just naming the notes on the fretboard, you can use either name. The scale context is a convention in music which says that you can’t use the two of the same note names when spelling out a scale.

For example, the G major scale has one sharp – F#, and the enharmonic equivalent is Gb. If we were to use Gb when defining the scale, we would get:

G A B C D E Gb

This definition includes the G note twice, and so is technically incorrect when spelling the scale. The correct spelling is:

G A B C D E F#

So it is really just a naming convention which prevents any confusion when spelling out scales and which allows us to define the key of the piece (as defined by the number of sharps and flats in the scale) when writing notation.

If you’re more interested in this side of music theory, look for a circle of fifths or chord wheel, which maps out the notes in a scale and their enharmonic equivalents.