Is this a "one-time" occurence? I mean, is this the first time you noted that you had to add "less than a quart" after 2500 miles?
If yes...I'd top it off when the engine and oil is cool up to the full "cold" mark and keep riding, checking it again later. It well may be that nothing is wrong at all, particularly since you've discovered the film on the frame is from the clutch cable.
On the older HD engines, prior to when Mother Harley started using guide seals, "normal" oil consumption was 300-500 miles per quart. Now, in reality a fresh early engine should be more in the range of 1000 miles, but if most of the riding was around town with lots of upshifting and downshifting it darn sure could drop to 500 miles.
In modern times, the "acceptable" range for an engine running guide seals, with everything in good condition, is 1000 miles per quart. But again, in reality these modern engines will generally consume a whole lot LESS than that, often without any noted use between oil changes, depending upon your mileage between changes. However, it's dependent upon riding conditions. If you tend to ride hard, winding that sucker out...particularly if you're riding conditions require more than a bit of agressive downshifting and accelerating...and especially if you ride somewhere that has extreme hot ambient temps...it may indeed consume a bit more and there is nothing "wrong" with that. Any HD engine will generally consume more oil when it's used for predominantly short rides around town and whatnot, when compared to long distance open road riding.
Also, as mentioned...if you just recently switched over to a full synthetic...that can add to the equation when combined with agressive, hot riding conditions.
If the HD tech truly said anything about "valves seating" he's in need of more training because valves are "seated" when they are properly fit/installed. Valves do not "break in"...not in any manner that choice of oil impacts. But then again, perhaps something he said was lost in the translation. In any event, at 13,000 milles that dang engine is as "broke in" as it's gonna' get.
If you ride in a typical manner...and if the engine continues to consume more oil than normal...the first thing I'd check is to determine if the air filter is oil soaked from excess oil coming out of the breather passages...the actual filter element, not just looking for oil inside of the intake tract...it may well be that you're having a carryover problem and the oil trap/umbrella valve in the rockers is not operating to its full capacity. Also...run your finger up inside each exhaust pipe outlet and give it a good wipe...the buildup inside of the exhaust should be fully dry...a little teeny bit "sooty" is OK, as long as it's minimal and dry...but if your finger comes out with any oily residue...oil is being burned, most likely getting sucked past a guide seal.
Don't freak out yet....as I started this post out with...it may be a single "one-time" anomoly with nothing "wrong" at all.