Yes this claim is true, songs are shorter now and TikTok has played a big role in that. Platforms like TikTok, and Instagram encourage artists to hook listeners fast, so this means the song starts faster, they hit the chorus sooner, ultimately making the song shorter. These platforms have contributed to shortening people's attention spans, by making short form content the most popular type of content in the world. These new trends have made new artists adapt and take advantage of this. In an article on this by The Washington Post it talks about how the average song length on the Billboard Hot 100 has dropped form over 4 minutes to around 3 minutes since 1990. So yes this claim is true songs are definitely getting shorter.