Reward of someone praying voluntary prayers sitting while being able to stand

The question: Is it permissible for the Mukallaf (sane person who reached puberty) who can stand to perform voluntary prayers sitting down? I have seen many of our Pakistani brothers, both youth and elderly, praying Rawatib (specific prayers before/after obligatory prayers) sitting down, even though they are able to stand. Once I asked one of them about this issue. What I understood from him is the Mukallaf is allowed to perform voluntary prayers while sitting even if he is capable [of standing]. And that his reward is like the reward of one who prays standing according to the Madhab (school of jurisprudence) of Imam Abi Hanifa. Is their claim true? Is this established in the Madhab? We hope you will benefit us; may Allah give you success. The answer: If a person believes that his voluntary prayer sitting down is better than or equal to his voluntary prayer standing up, then this is a mistake because it is contrary to what is established in the hadeeth of the Prophet ﷺ: that the prayer of the sitting is half of the prayer of the standing. But if they do that as a form of taking the concession, while believing the reward is only half the full reward, then there is nothing wrong with it. That is because the standing is not a Rukn (pillar) in voluntary prayers, rather it is only recommended and virtuous. But what still requires consideration is, if they sit in the Rawaatib, will they get the full reward of the Rawaatib? The answer is no, they do not get the full reward of the Rawaatib. Rather they only get half the reward of the Rawaatib if they are not excused [for sitting]. As for this being established in their Madhab, I do not have any knowledge regarding it. In any case, even if it is established in the Madhab, what goes against the hadeeth of the Prophet (ﷺ) is not accepted, regardless of who decides it is established.