uBOL is entirely declarative, meaning there is no need for a permanent uBOL process for the filtering to occur, and CSS/JS injection-based content filtering is performed reliably by the browser itself rather than by the extension. This means that uBOL itself does not consume CPU/memory resources while content blocking is ongoing -- uBOL's service worker process is required only when you interact with the popup panel or the option pages.

uBOL does not require broad "read/modify data" permission at install time, hence its limited capabilities out of the box compared to uBlock Origin or other content blockers requiring broad "read/modify data" permissions at install time.

Emphasis mine. No background processes, including a website-reading permission does indeed sound more optimized for mobile, where people may have limited resources.

On lower end smart phones? It probably just slows the phone down less specifically because of how few processes it uses in the background. But I don't know. I'm not a lite UBO user. It definitely doesn't have the same number of features as the regular variant of UBO though.