First off, I admit that I was sooo far behind on threads that I've given up and skipped to the last post. So forgive me if this has been speculated earlier.
Regarding the reverse ferret Megxit in late August, it could be possible that she had gotten word that, as a result of TMJr's discovery and subsequent report to authorities, there was an investigation starting (or going on) into her father and she either had been or was worried that she would be contacted by the relevant authorities as to 'what did she know, and when did she know it?' and was concerned about allegations in the 2018 letter which she kept silent on. I'm not suggesting she would be anything other than her being approached as an innocent party asked to provide information. But I have a feeling that the last thing HaM would want would be for either of them to be involved in a police investigation of that nature in any way, shape, or form, let alone any damning information should that 2018 letter come to light.
The US authorities weren't going to 'protect her' from other authorities, but perhaps HaM believed that, 'as royalty' the UK authorities would. May also be another reason why they desperately want RAVEC protection.
It's also quite possible that 'the 2018 letter' itself was written by a family member (Samantha's letter at the KP gates?) as a plea to M to either 'tell what she knew' or to 'come to their father's defense'. I'm sure that any letters, especially one handed over at the KP gates from an estranged relative, would be screened for contents and then handed over to the appropriate person to give to the Royal involved. If this letter does contain a plea to defend him against CSA allegations, it will be damning.
FWIW, as far as I can tell TMSr's residency dates are:
2011 retired, moved to Mexico
2017 reported still living in Mexico
2025 moved to Philippines
2026 returned to Florida, USA
My feeling is that his move to the Philippines in 2025 may have been prompted by an investigation by the Mexican authorities who may have contacted US and Philippine authorities. US authorities may have been contacted if he had kept any 'ties' to the US. And chances are he still had US bank accounts.
Or it could all be bollocks on the part of TMJr. Who knows at this point.