I found new chunks in my world and also two sea turtles that spawned on a beach. I gave them both a sea grass in which they both entered love mode. After, one turtle got bigger but it did not do it's digging animation nor did it lay an egg. All that turtle did was return to the ocean and swim in circles.

I've also tried to breed two turtles in a brand new world and got the same result, no egg laying.

I'm on PlayStation 4 bedrock