While an OD rule is intended to make boats similar it doesn't guarantee that boats are identical. Several changes are allowed under the current rule that could make consideralble differences in boat speed. Here are some.
Sail maker and sail cut can have an impact on boat speed. Rig tuning, bottom surface, keel fairing, age of sails, moving and double ending the backstay adjuster, carbon fiber pole, cutting the cover off of halyards - all could provide incremental inprovements in boat speed. How about "dry sailing" the boat vs wet sailing. This list could get pretty lengthy but what's included above should make the point.

Some OD events try to level the field by using one sailmaker and by making the competitors rotate boats in a regatta. - J/30 OD events do not. Therefore, J/30 boats that show up at an OD evernt are different - not the same.

For purposes of the discussion let's simplify the quote to "how do you win a sailboat race? - Start with the fastest boat"

So, back to relavent comparisons; do the front of the fleet sailors, pay attention to most, if not all the details of making the boat fast before leaving the dock? Probalby, and if so why?
Most likely because they want to "START WITH THE FASTEST BOAT"

Regardless the point of starting with the fastest boat was made in regards to an earlier post that said one bad tack would offset the benifits of a string sail. And to that point, the idea, I think, is not to make bad tacks. But, If a bad tack happens, I'd rather have a boat tha can accelerate out of the tack faster - which leads us back to string vs. Dacron