Classical scholars also appealed to early Muslim practice: sinful people who still belonged to the community were, in general, treated as eligible for funeral prayer, supplication, and asking forgiveness, even when their serious wrongdoing was known. This weighs against declaring every major sinner an unbeliever.
The argument does not eliminate every juristic exception relating to funeral prayers, nor does it provide certainty about every individual inner state. Its focus is the continuing general treatment of a Muslim who has not been established to have left Islam.