/clone command Block Limit Not Working

I was building in my creative world, and I wanted to clone a large building. Usually, there's a limit to the number of blocks I can clone (32,678 or 2^15) but the number of blocks I cloned ended up being over 40,000, much higher than the block limit. I recorded a video of the bug as well as my settings.

Video link: https://youtu.be/HH27q7pOhYo

The issue might be due to a high memory usage on my computer (I have like 30 tabs open) but I can't see how that would affect Minecraft like this.