`$effect.tracking()` is inconsistent for custom transition function

[Azarattum]

Describe the bug

Fro intro it is true, for outro false.

function customTransition() {
  console.log($effect.tracking()); 
}

<div transition:customTransition>clicks</div>

Originally reported here.

Reproduction

https://svelte-5-preview.vercel.app/#H4sIAAAAAAAAA11OS26EMAy9SurOAiQ0dM0EpLnD7EoXTHCQNcFBxCBVUe5ehX7VhSX7-f0iWHIYoHmNwMOM0MB1WaACeV_yEXZ0glBB8NtqMqKDWWmRrudeHIraKdDdoWrVKcggWLyUl_zLYzc2Qp6V2YL4-bYOHCgDRaniQRLjOXiHZ-en4oTWopGzrIN5EE9FWV5UpqWedf2by_q-iXhWno0j82hjUaq2-1Pl6WtN3c1Pk0NdfyoOdXwm-81N2V6PtCv5Kdf8b9sdKUHXI-1dz7Emm6CC2Y9kCUdoZN0wvaUP1krN5U0BAAA=

Logs

No response

System Info

n/a

Severity

annoyance