Descending it still be a pluck. Only time it’s a no brainer if it’s a pull off to open string.
Although descending while tapping it’d be a higher string.
Like tap g string 12 and left hammer 11 9 7 slide to 5 pluck b open
Continue tap d string 7 left hand hammer 5 4 2 etc.
The same works great for say a e blues box lick in 12th fret. Descend from e string down any way you like. When you get to 12th fret d string the next note works be b on a string 14th fret.
Instead pluck that note as open b strung and continue down open position e blues box lick
That will buy you time to shift positions without tripping over your hands.