Why is the note link tappable in Apple Reminders but not in Google Tasks?

It comes down to what each app allows. Apple Reminders auto-detects the note's link and makes it tappable. Google Tasks and Asana won't make that kind of link clickable in their notes, so by default they show a plain "Note saved at: …" path you can find on your Mac. If you want a clickable note link in Google Tasks, turn on "Upload notes as PDFs (Google Drive)" — that uploads the PDF to your own Google Drive and puts a real, clickable Drive link in the task. In Asana, turn on "Attach notes as PDFs" instead — the PDF is attached directly onto the task.