We all have different methods to get to the same place. The wave washer holds it in place but if you accidently press too hard against the bolt and drop it part way out it sucks, just like a broken pin.
I use scotch tape on my gauge, with ejector in it has a tendency to "tear up" the tape. I like it very snug on the gauge with 1 piece of tape. With two thickness it is no go. This method has worked for me to get all 5 of my 6.5 CMs close enough to use same bump setting + or - .0005. So it definitely works for my purposes.
However i have set many with complete bolt intact with no consequence. I still double check no go with 2 tape layers (approx .004). Some tape brands vary up to .0005 so best to measure each use.
The "stripped bolt" method can also be used for checking bump on sized brass and where the bullet meets the lands. For checking bullet in the lands the rear baffle has to be used with the detent balls removed. The PE is required to feel the "click" as the bullet is extracted from the lands. The baffle can be lightly taped to the receiver to keep it from flopping around.
If interested it is called the "Wheeler method" and there is U-tube video of it. (Done on Remington or clone).

Edit: the wave washer also adds a small amount of tension between the front baffle & bolt head. Part of the reason for reinstalling the "unloaded" firing pin. The bolt will not fall free with the wave washer in place.