I don't know the answer but it seems that even the tip shown when you place your mouse over the BS button, shows the beams like that...
I guess the other way is to use arrows... or use single beams at the boundary line.

GOTCHA! I have A solution, maybe not THE one, but....

I've set the layout rule as "Maximum spacing", and set a value.
Then I've edited the boundaries, and offset the end and beginning lines from the same value I've seen in dimensions, outside the previous limits.
And now I have a beam at the very end and at the very start of my BS.:thumbsup:

How proud I am!

See pictures bellow. :wine:

The beam system tool is setup assuming you only want secondary beams, and you already have primary beams i.e. a typical floor layout with main beams at columns on grid and you just want to infill inbetween, therefore not needing beams on each end

The workflow you have used will work, but the problem is if you goto select the beam system your boundary extends beyond the zone you would expect.

For joists this workflow may work, but for purlins I normally just copy the last beam into place because having the beam outside the beam system is a requirement anyway, since the purlin will switch orientation at the box gutter or ridge line which you cannot do if part of the beam system

For the spacing you can only specify the setout point with the layout rules "fixed distance" & "clear spacing" in these options I would suggest using a justification of "direction line" which is easier than editing your boundary IMO

But it has been a long standing wishlist item to have an option to include beams at the start and end of the beam system.