Lore help
Maybe it’s the sylvari in question’s Wyld (ugh I hate that spelling) Hunt to learn as much about non-magical methods of doing things as they can. Or they just don’t like magic, much as the Nightmare Court rejects the teachings of Ventari.
There’s a lot of ways you can reconcile it, if you really must reconcile it at all.
If you are looking for RP reasons, you can go with anything. Maybe your sylvari is less attuned to the Dream and the magic of Tyria as a whole. Maybe its a conscious desire to distance themselves from both, making them soundless AND an engineer. Or maybe its just a matter of talent, just like they could have affinity for thievery as well as swordmanship or mesmerism.
Technicly sylvari dream of the world before they wake up, and depending in what they see in this dream, they can have varying interests. Seeing the technological progress on Tyria in the last decades/centuries, it should stand to reason that more and more saplings dream of machinery and craftsmanship.