There is nothing in the SECURE Act that affects this old of an inherited IRA.

"If I understand the changes correctly under the Secure Act, non-spouse beneficiaries can no longer take that option and must disburse the funds within 10 years?"

That applies for someone who dies Now. Not back in 2017. Your client's IRA has already passed to this person.

Just like someone who was already 70 1/2 and taking RMD would not then completely stop and start again at 72 (setting aside that everyone gets a forgiven skip year of 2020), just because the new start date is 72.