Sad ly it was a legal play. Thomas did make a football move after the catch,and there is no targeting rule in the NFL.
That's only in college.
https://www.nfl.com/news/nfl-says-hit-by-niners-whitner-on-saints-thomas-was-legal-09000d5d82606878
edit- I should have said no targeting rule that year. The NFL does have a similar rule now.
https://fansided.com/2023/01/14/nfl-targeting-rules-penalty/