tab witch should fix errors in commands doesnt fix uncapital letters

What I expected to happen was that tab will fix uncapital to capital letters

What actually happened was it didnt fix the mistake.
I was writing a command in chat what i copied from the internet and to check for mistakes i pressed tab nothing happened so i pressed enter and it shower that it waas previded in a invalid format.

1. write a command in chat for exaple:/summon lightningbolt.
2. press tab, you will see nothing happened.
3. press enter.