My aspie daughter had a really difficult time with tense, pronouns, time reference etc. She still will say, "I told you today," meaning yesterday, or when she's talking to her older sister, she will say, "no, my mom said no," when they both have same mom.
I don't think it's echolalia, I just think we take for granted how confusing English is, and they are literal, and the grammar rules are not consistent. Be patient, and gently correct. It takes time, but they get better and better at it.