If your only adjusting the play in the bearings then the gap your removing will be thousands of an inch and not mm. I wouldn’t even bother slackening the punch bolts. Make your adjustment on the castellated adjuster then refit the top nut.
If you decide to drop the forks out, removing the top yoke and castellated adjuster will allow this. If you have no history of the bike then it wouldn’t be a bad idea to check the condition of the races and re-grease. You could also check the condition by removing the slack and ensuring that there is no play by pulling on the fork sliders. but ensuring that the forks can still flop side to side. And check for any roughness will indicate new bearings required.
Now let’s all have a beer
68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (now rebuilt)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)