Currently, if you select a machine, then select multiple relevant fixlets for that machine, right click and take the default action, you will need to re-select the machine that you want to take the default action on.
However…
If you select a fixlet, select multiple machines, and take the default action, those multiple machines will auto-populate and you don’t have to hunt for the machines (still need to highlight them).
I will file this request. This behavior has changed multiple times in previous versions because of customer requests, which I think is why you see slightly different behavior in these different situations.