Some jailbreak tools (like Checkra1n or palera1n) have pre-installed stub versions of AppSync. Repositories often refuse to install due to "already installed" conflicts. Installing via using dpkg -i bypasses these front-end protections, allowing you to force-install the exclusive build.
Standard releases hide certain debugging flags. Exclusive builds often leave DEBUG=1 and LOG_LEVEL=3 active, allowing advanced users to monitor installd in real-time via syslog. This is invaluable for developers testing custom IPA signing tools. appsync unified deb file exclusive