There are also other cases: A trill with written-out termination whose slur ends before the note that follows.
But even a 32th note can be played staccato if one takes a bit more time for the pause between first and second note. I would play it like that.
But why would you separate 16th notes, for example, under slurs that stop at the end of each beat or at the bar line?
Okay, there are several shades of "separation". Or the other way round: several shades of legato. It's even possible to play non legato or staccato notes in a melodious manner. So separation means at first: begin something new, if you leave the key or not isn't the only criterion.
I don't think you begin something new when you separate 16th notes, under slurs that stop at the end of each beat, or at the bar line.
So as I understand you now, you ask how to play legato slurs in Haydn's music, and the only allowed answer is: ignore them! ?
observing the ornamentation practices of the period, play the line or phrase as musically as you can.
Similar slurring exists in the opening phrase of Mozart's Rondo K.485. The Scerzo of Beethoven's Sonata op.2 no3 presents an analogous situation. Some pianists find it convenient to continue each upbeat slur over the bar line, making the first separation on the staccato note.There are some situations in which individual slurs may not always indicate an attack and a release and where the legato may properly continue over the bar line even though the slur ends before it. Logged
Remember that slurs were often used to indicate groupings, not articulation or stresses, and for a pianist, it's more easily grasped if we have an image of a string player and his bow-markings.
Topic: Opening of Haydn's sonata Hob. XVI: 30 