Was the practice of some of the Salaf, such as Ahmad, of acting upon weak hadiths based on a concept of "weak" that differs from the currently prevalent understanding?

The discourse of the Hanbalis is the authoritative source for understanding the principles of Imam Ahmad's madhhab. They hold that Ahmad ibn Hanbal would accept mursal and weak hadith if there was nothing to contradict them, preferring this over qiyas (analogical reasoning). To him, a weak hadith was not false or denounced (munkar); rather, it was a category of hadith. If he found no tradition or saying to contradict it, acting upon it was more preferable than qiyas. The Imams agreed with him in prioritizing weak hadith over qiyas. As for Ahmad's choice between fiqh (jurisprudence) and hadith, his intent was not to limit oneself to merely narrating hadith without understanding and comprehending its fiqh.