A glitch called "gravity block conversion" was discovered a while back but it's now viable thanks to SLH. The glitch allows you to convert regular falling blocks (sand, gravel, etc) to any random block in the game -- including the end portal. The odds are not particularly favourable, around 1 in 3000, but it is possible.
Now, why do we instantly go to the credits upon entering the end portal? Well, while turning back into a solid block, it is still a falling block, leading it to enter itself (effectively duping itself in a loop), which is why you can see another end portal at 0:40.
Seed: 110236978
Version: 1.12.1
Update (27/7/24)
New WR by guccigang (www.speedrun.com/mcbe/runs/mk133qvy)...