I struggled for quite a while to try and get the blade adjusted
parallel to the miter slot. Thinking I had a Delta Unisaw (purchased
second-hand), I loosened up the 4 bolts that secure the tabletop to the
cabinet and tap-tap-tapped. I couldn't get any adjustment.

I phoned Delta and it turns out that I don't have a Unisaw. Mine is a
10" Cabinet Saw 36-750 sold in Canada. This is similar to the Hybrid
saw they sell today. The trunnions are mounted to the tabletop.

Amazing! I was able to get the blade within .001" using my new dial
indicator. It sure makes a cleaner cut. I was seeing alot of burn
marks cutting 3/4" melamine with a crosscut sled. Now there is no
burning.

Now, the Delta Tech explained that I should clamp each of the trunnion
brackets to the tabletop before loosening the trunnion bolts and
adjusting. Does this make sense?

I did not do this clamping step. I found that it was very fiddley. No
matter how hard I'd try to keep the blade in alignment during the
re-tightening of the trunnion bolts, when I final-tightened the
front-right-side bolt, the blade skewed such that the back of the blade
was closer to the left-hand side. The only way I finally got it into
alignment was to start off with the blade an equal amount skewed to the
right side, then tighten up the bolts. It finally came out within
..001"

Do I need to re-do the whole alignment now that it is aligned?

Would the step of clamping the trunnion brackets have prevented the
assembly from twisting during the tightening?
Thanks for your help.

Mr Fixit eh