What are the chances of needing root canal treatment after getting a crown?

My new dentist said that there’s a 20% risk of needling root canal treatment after getting a crown as it could irritate the nerve, my risk elevated as I have a crack (filled but didn’t work, hence needing a crown) and want a porcelain one (more drilling). Just wanted a second opinion on whether this 20%+ figure is correct? This is a lower molar. The dentist is a general dentist who’s been practicing for ~6 years.