Still not sold...here's another sales pitch.
The engine is inclined in the chassis, so gravity will tend to move the crank rearward. The crank, therefore, spends most of it's time riding gently on the front thrust bearing. Now you go to engage the clutch. First the free space must be taken up between the clutch forks and throw-out bearing. Then the throw out bearing picks up the crankshaft and must drive it forward until "clunk"...all the thrust play is removed. Now the clutch can be disengaged.
If the thrust clearance is .006". you will never hear the "clunk" engaging the clutch, and the crank will never make an audible knocking from end play. If you approach 1/8" thrust play, then you are significantly affecting the clutch throw available...and you will notice the "clunk" regularly when the clutch is engaged. 1/8" at the clutch is more than all the clutch fork free play available in a well-clearance engine/clutch. Later you my be wondering why the clutch drags, even though all the settings are spot on.
So far we assume everything else is spot on. If you have a cocked rod or piston, the endplay knocking could be constant at idle and low speeds.
If I have to worry about an excessive clearance for more than 10 minutes during an engine build, then that is a sign I need to make it right! If you have been concerned for more than 10 days and you leave the clearance large, then you will always wonder...!?! It's a cheap, readily available bearing. Why give it another minute's thought?