NO - synthetic oils do not cause leaks or cause leaks to get worse. The AutoRX has cleaned any sludge & varnish away from an already present leak, causing the current leak. Synthetic oil will not make this any worse.
However, if the leak persists, I would attempt the second autoRX treatment in an attemp to swell the seal and reseal the leak. From the way you descibe it, with autoRX loosened the junk around the seal, but didn't get to the seal.
Frank would be the better person to decide if a second treatment is needed, but I'd bet he will advise the use of a second treatment.