My boyfriend [28F] created a fake instagram account for me to see [26F]

My boyfriend (28M) and I (26F) had plans to hang out on Sunday. Throughout our relationship, he always described himself as the most humble and trustworthy person and often said he would never lie to anyone. Up until that point, I believed him because I had never caught him lying before.
We had been together for an year, but we never followed each other on social media. I rarely use my Instagram, so it never really mattered to me. On Sunday, we went on a date, and he took a picture of us holding hands. He told me he was going to post it on Instagram, and I replied that I would follow him.
I don't know whether he created the account right then and there or if he already had it prepared, but instead of showing me his real Instagram account, he showed me a different account that had zero posts and zero followers. It appeared to be a fake or burner account.
What made this strange was that I already knew what his real Instagram account was because he had sent me videos from it before. Whenever he sent those videos, Instagram would give me the option to follow his account, although I never bothered to because I didn't think it was necessary.
So when I asked to follow him, he didn't show me his real account. Instead, he showed me this empty account. That immediately raised concerns for me. Why would he do that? Was he hiding something?
When I confronted him, he said he didn't want me to see certain pictures he had liked while he was single. According to him, that was the reason he showed me the other account.
I'm not sure whether that's a reasonable explanation or if there's something deeper going on. What should I think?

TL;DR: He created a fake Instagram account, and that's when I started questioning things.