I would say the answer is: yes, but…
If you add or remove material from the arrow it will change the spine. The problem is in how you measure that change. The technique we use to measure spine is to support the arrow by two points separated by a known distance. Then hang a weight between the two points and see how much the arrow bends.
By removing part of the arrow as we taper it, we have changed how the arrow will sit on the 2 points. It will naturally be lower now. In addition, where we choose to measure the arrow will affect the reading too. Measure closer to the back and the arrow will be weak. Measure closer to the front and the arrow will be stronger.
So the standard is to measure the spine before tapering. Taper the arrow, then shoot and see how it goes. When you buy tapered arrows, they are grouped and sold by the spine measured before tapering.