Yes, this was a Phuket Immigration Office-specific policy to grandfather those having continuously held Non-OA visas and extensions from before the mandated insurance requirement came into effect.
Phuket Immigration had been an outlier, allowing those who held Non-OA visas or extensions from before the effective date of the change to continue under the old rules. That is, they were grandfathered from the then-new mandated insurance requirements. One of a few immigration offices to adopt that position. Sad if they have changed this long-standing policy.
Online 90-Day Reports are accepted from 14 days before the due date up until the due date. At least that has been my experience in Phuket. After that, in-person applications are accepted up to 7 days after the due date (strictly including holidays, weekends, or other days the office may not be open). The drive-through in Phuket Town offers excellent service and you can also use the other satellite offices in Patong and Blue Tree.
My understanding is that all US passports obtained through US Embassy Bangkok come with 50 pages automatically. I don't think it's possible to request extra pages. 50 is the maximum, I believe. I don't think you even need to request 50 pages as it is the only size they offer through that site.
The central requirement for a retirement extension (so-called) is that you be age 50 or older. If you are not there is no way to get this extension, no agent can finesse this requirement.