Absolutely. It rebuts the worry or the presumption that partisan self-interest is the only motivation for a particular proposal for reform. If the governing party selects a reform option that is not optimal for that party's political success in a future election, then from a legitimacy perspective that would certainly be viewed as being a more principled decision than a decision that was clearly self-interested in the sense that it would enhance the governing party's political success in a future election.
Therefore, yes, I think to make a disinterested selection would add to the legitimacy of any proposal by a governing majority, which is why it is so important to make sure the process is, in fact, both fair and perceived to be fair. You don't want a situation in which successive majorities cherry-pick rules that help them, and then the next majority comes along and picks its own set of reforms that it can push through because it has a majority power in Parliament.