Non-target projectiles cant be seen in the fog of war, like mirana's arrow here for example.
However, Tinker's missles are seen for the enemys at the moment tinker fires them, revealing tinker's current position.
This affects gameplay in a huge way, as the enemy can jump on tinker knowing his position.
When viewing a replay from the tinker's enemy perspective, the missles vision works correct, but when playing in-game its broken.
Heres a video I made demonstrating this: