I have noticed many new songs are shorter in general (around the 3 min or just under mark).

But on your point on Lizzo's about damn time, the song/second verse was definitely not written for TikTok. I will have to look but Ryan Tedder (OneRepublic) gave an interview on that song that was very interesting. IIRC, About damn time was commercially a flop in its first few weeks and wasn't performing well, until someone made a tiktok dance for the second verse which went viral, in turn pushing the song. it was a really interesting video

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Not the full interview but its most of it:

https://www.youtube.com/shorts/vPo1qgsNvUI