Exploit or glitch, where you can get achievements in creative?!

When you start a normal no cheat world, then activate creative in that world, and give yourself 2 command blocks and buttons, put the 2 command blocks down. The first one, the command is: /gamemode c @a . And the second ones command is: /gamemode s @a . Then you put the buttons on the command blocks.

Then you leave WITHOUT SAVING (so leaving minecraft) and come back to that world. Then youll be in survival, then you press the button that gives you Creative. 

After all that, you can get Trophies/Achievements easily with creative. I find this unfair.

This exploit or glitch was in Youtube and the video had 100k views, and thats just that one video i saw. Theres a lot of more videos explaining this exploit. 
Thank you for fixing this if you see this👍

By the way, i dont know since when this is possible, but its still working in this version. Idk the version im were on.(If my text is not understandable, sorry)