Trying to stop flying in Creative by double-pressing the space bar (or whatever other key is assigned to "jump") triggers elytra, making a direct transition from Creative flight to elytra flight. This might be useful in a few cases, but usually it's not. It's also different from how it behaved before.
According to MCPE-145317, the fix for this bug wasn’t included in Bedrock Edition when the ability to activate elytra while ascending was added.