ADVM—While dose de-escalation is pretty common in a phase-1 trial (e.g. the standard "3x3" design), what we have with ADVM is unplanned de-escalation following a clinical hold. That's an altogether different story that warrants the skepticism shown in the tweets you cited.
“The efficient-market hypothesis may be the foremost piece of B.S. ever promulgated in any area of human knowledge!”