The Qurʾān is the foundational scriptural source. An important question is the level at which particular recitations are established. A canonically transmitted Qurʾānic reading and a reliable but non-canonical reading (qirāʾah shādhdhah) are not assigned identical textual status.
Some Hanafi legal-theoretical discussions allow a reliably transmitted non-canonical reading to inform legal reasoning in a role comparable to a report or interpretive transmission, without declaring it a canonical Qurʾānic recitation. Whether wording counts as Qurʾān and whether a transmission may be useful as legal evidence are distinct issues.
Schools differ in the treatment and strength of this material. It would be inaccurate either to identify every such reading as decisively established Qurʾān or to assume that jurists can never treat a sound transmission of it as relevant to interpretation.