Hi buddy,
First of all, well done on picking up on this. Not many people do. 👌
Gelato does in fact change its smell during flowering. Whereas it starts smelling of what can be described as sweet, even punchy citrus in the beginning, the smell changes to what you describe as "thyme", a sweeter, more floral, and almost creamy sensation.
That's a very good sign as she ain't called Gelato for nothing. It is these creamy, sweet terpenes that make Gelato such a hit.
How do I know? I just harvested a very yummy smelling (and tasting) Gelato a couple of weeks ago.
Grow on,
Jeff Weedy 😎