Not speculative at all. It’s very well documented.
Not only has the SAHP put the breaks on the career trajectory (usually during the most important years), but staying out of the workforce for even a few years will affect things like vesting for retirement or other benefits, service credit for retirement (for jobs with defined benefits), continuing education/licensing requirements, career experience, outdated knowledge when re-entering the paid workforce, etc. In the vast majority of cases, it will PERMANENTLY affect the SAHP’s income earning potential.