The Package Support Framework (PSF) is one of the most important compatibility tools in the MSIX ecosystem. It enables legacy desktop applications to run in MSIX by placing a launcher and runtime layer in front of the application, applying fixups, and optionally running PowerShell scripts before or after application execution. That same flexibility creates a governance question: how much additional user and operational risk is introduced when PSF is used, especially in App Attach environments? This paper concludes that PSF is not inherently unsafe, but it must be treated as a trusted, full-trust compatibility layer rather than a routine packaging default. A controlled positive test showed that PSF start scripts can execute under interactive activation when built with the official PSF runtime, while non-interactive automation under-reported script execution; install and launch success alone should not be treated as evidence that configured scripts ran. The highest risks are script governance, broad full-trust desktop-app scope, detour/fixup behavior that is hard to inspect after deployment, supply-chain injection before package signing, and App Attach launch-time sensitivity. The recommended defensive position is evidence-based use: prefer native MSIX first, add PSF only where runtime evidence proves it is needed, sign and inventory all PSF binaries, treat scripts as managed code, protect the signing and packaging pipeline, and validate App Attach lifecycle behavior on production-equivalent hosts.