Two cases may look alike without sharing a cause relevant to the legal ruling. Qiyas requires an attribute recognized as a legally effective ʿillah, not simply visual or linguistic resemblance.
For example, two actions may both occur within prayer. That does not establish that both have identical effects on ritual ablution. A special ruling for one act cannot automatically be extended to every act merely because each happens during prayer.
Test: Identify the authoritative ground of the ruling. Establishing qiyas as a valid legal method and proving that a particular analogy is sound are distinct tasks.