The article discussed how a piece of rock could be ejected from Mars and land on Earth without ever getting hot, but I’m wondering whether living cells or even spores could survive the acceleration involved.

They can, the experiments have been done! Melosh (the guy I cite in the article) fired B. subtilis and D. Radiococcus spores from a rifle(!) and established that the acceleration and jerk aren't a problem, at levels far higher than the panspermia mechanism needs.

https://repository.geologyscience.ru/items/4b405174-0734-474...