What is it with "Lag"

Every now and then when I play comp, I get this one tank player who always instalocks sigma and refuses to swap and claims its “lag”.

But does lag really make you charge in alone when everyone else is telling you to regroup and fall back? Does it?

Does lag make it IMPOSSIBLE to swap off sigma when its clearly not working? Does it?

Does the lag make you type ‘‘ggs no heals’’ after one team fight is lost? Does it???

Does it make you purposely throw my comp games? Does it really?

Can anyone who deals with lag please let me know if this is really what lag does to you guys?