Shulchan Aruch Harav Orach Chaim 473:48 says we don’t need to stand during hallel
לְפִי שֶׁכָּל מַעֲשֵׂי לַיְלָה זֶה הוּא דֶּרֶךְ חֵרוּת, לְפִיכָךְ אֵין מַטְרִיחִין אוֹתוֹ לַעֲמֹד.
How come, according to SA”H, in expressing our freedom we don’t need to stand during the Seder Hallel in order not impose on others, yet by heseibah which is also an expression of freedom and a halachic requirement we DO impose on others in requiring them to lean (of course those who are halachikly required to do so)? Leaning while eating (especially if you hold of the opinion that it be done throughout the meal) might even be more of a tircha than standing for hallel. It may not be the most comfortable or convenient way of eating.