Is it normal for a friend to tell a friend not to move in with boyfriend?

This isn't about me because my boyfriend is American like myself but my friend Amy whose boyfriend is from England was upset by something our friend said and we're trying to figure out why this was said.

We were all out to dinner last night and my friend Amy said she's going to eventually move in with her boyfriend either here or in England. I said that's a good plan but our friend Liz immediately responded with something like, "you don't have to move in with him" and had a very wide-eyed, serious look on her face. Amy then responded with, "well eventually, I will". But Liz just kept telling her that she doesn't need to move in with him and that they should keep it long distance until a later time because it's better to wait. Amy kept telling Liz that was the plan but Amy is very serious with her boyfriend and has been with him nearly a year now and Liz knows that.

We can't figure out why she said this. I got annoyed as well and told Liz that Amy should move in with him sometime in the next year and Liz still disagreed saying that's too early. How is a year later too early? They would then be together for two years which would be safe to say they are committed enough. My boyfriend and I are looking at apartments but Liz hasn't said anything about that and I've only been with my boyfriend 8 months. When Amy went to the bathroom, Liz literally said something like, "I can't believe Amy is going to move out so quickly. She really needs to take it slow" and I remained silent while she kept talking about how "bad" it is to move out.

is it normal for a friend to say this? Is this because she's single and has never been in a relationship that lasted more than three months before?