Never tape or restrict a finger for this purpose. What you have is a standard little finger movement that has not been developed.
You have developed lifting your little finger up and away from the fretboard using the large knuckle, rather than retracting it.
Next time you pick up your bass retract your little finger away so that it curls the fingertip back to the palm at the base of the finger (or as close as you can). This means you are using the joints correct so tension flows through the finger joints rather than over them. Most of this type of problem can be attributed to action of the large knuckle with no finger joint bend.
Try it on a table if unsure of the movement.
1/ Place the hands and finger as if playing a piano, so that's palm down, fingers with a nice curl and all fingertips on the table.
2/Without lifting from the knuckle first, curl the little finger back so the fingertip is tight to the base of the finger. Notice how the first finger joint is now higher than the back of the palm this requires tension on both side of the hand.
In this action the big knuckle lifts up due to the influence of the finger curl to allow the fingertips to move away....it does not action the movement.
Even if the fingers are flat on the table the principal is the same, the little finger curls back rather than lifts.
In this example you will feel the ring fingers influence on the little finger. In each example compare the lifting off action against the retraction example.
Notice how when you lift off, the finger is straight, because the finger joints are not involved, it is only the knuckle that is working the action over the top of the joints. This action happens because to lift a finger the action of muscles deep in the forearms and tendons have to pull the ligaments on the back of the hands to lift. Where as to curl, it is the same principal but you use the opposite side of the hand so the fingers do not lift but curl. What you and other see in this little finger movement is the result of using the lifting action rather than the curling action.
Ring finger and little finger share certain tendons so they are linked, that's why taping them together never works....they already are "taped" together in a sense by the ligaments.
The lifting action and the curling action both move the fingertips away so it is a blend of the both......how well you do it depends on how well your hands are.
