During the first versions where this sound when present (Alpha v1.2.0 - development of 1.3), it would play during the loading screen for the Nether. However, when added back in 1.9, it instead plays once the world is fully loaded.
MC-212651
Portal travel sound plays too late
Resolved
Invalid
2
This isn’t invalid. Should be reopened. Could also be considered a parity issue as Bedrock edition has the travel sound play as the world is loading in just like Java edition prior to 1.3.