you're right...i'll try to rephrase...

this is pentatonic:

--------------------5-8-----
----------------5-8-----
------------5-7-----
--------5-7------
----5-7-----
5-8--------

you will surely know this...

but there are more pentatonic scales than this.

You can also start this at a different string, which chances the key...i know that.

But...

This is only 1 possible pentatonic scale. why does one choose this one, or another pentatonic scale?

you could use the scale above anywhere on the fretboard (in the correct key),so why would anyone another pentatonic scale if this is correct as well?

thanks,