I’d heard this idea years ago. There really was no evidence that the voyages spread syphilus in Europe. Some people just liked the idea.
On the flip side there was no evidence that Europeans spread tuberculosis in the New World either. Later on it was proven that tuberculosis has been in the New World for many thousands of years.
There’s plenty of evidence that syphilis was not present in the “old world” prior to 1492. It’s well discussed in another topic around here (linked above). It poses a bit of difficulty for those like me who recognize the evidence for a great antiquity for oceanic navigation. Syphilis appears to have been homegrown in isolation in the “new world”.