NOTE: This is behaviour detected in a modified world where I used NBT editing to give myself an end gateway block, placed it down in the overworld, used NBT editing to modify the teleportation target, and then tested in Android Bedrock.

The intention was to replicate the Java functionality found in this youtube video
https://www.youtube.com/watch?v=TcTlv6_vjWQ

The result was that when placed, the beam activates and the block is shown. However, when a pearl is thrown into the portal, the player is not teleported to the target coordinates specified in the NBT data. The player remains at the point of origin.

Also, the flag for isMoveable appears to be set to 1 (true) by default when placed, making it so that the player cannot walk into the end gateway block as shown in the video.

When the block is placed and checked with NBT editor, the integer field values for x, y, z  are populated with the exact location of the portal block and the exit position flag set to 1 (true). The integer field values for ExitPortal x, y, z default to 0, but if modified, these should be the target location to which the end gateway should teleport the player when entered/pearl thrown into gateway block.

IF the entire portal bedrock structure is created around the end gateway block, the result is that the player begins to suffocate when a pearl is thrown into the gateway.

I submitted the question to the minecraft discord (technical-bedrock) channel and it was tested by Jira Bug Tracker user Gruva [guy] and similar results were detected.

I am including a screen capture from Blocktograph of the NBT data values for the placed end gateway portal. Expectation is that the player should be teleported to 484, 70, 10000 if the player enters the end gateway block located at 384, 70, 10000.

Testing was performed both with and without the surrounding bedrock structure blocks with the only difference being suffocation if the structure was added. Testing was performed in the overworld upon multiple instances of placed and edited end gateway blocks.

Testing was done both WITH and WITHOUT a end gateway block existing at the end target location, however, according to the youtube video for Java, on that version it does not matter if the end portal is there or not since all data should be self-contained within the teleporting end gateway block.

No issues discovered with generation of natural end gateway blocks within The End, however, values were compared for reference and confirmed correct values were being placed for each NBT field.