Incorrect, it has always been this way. Maybe you have just been lucky and had loans taken out for the full time, but it's been like this for almost a year.
Then I must've been super lucky. Thus far when I have lent for 30 days, it always said "30 days". Now, since today, it was "2 days" and "5 days". During the past year I've lent at least a hundred times, probably more. It is possible this could have slipped through me a few times, but if it was often, it would be impossible not to notice.
I too have noticed this since a few days and it's never happened to me before (since i started on Bitfinex in February). So it happened to both of us at around the same time. That does not seem like just coincidence. Maybe the bfx team did change something on the site and didn't announce it?
Normally the duration displayed in "swaps currently provided" would be excactly what i entered when i created the offer. Once taken, it would then disappear/expire whenever the trader decided they didn't want it anymore. Now it seems like traders can set the duration beforehand? I'm not familiar with the margin trading interface, can anyone confirm?
edit: and now, three of my taken offers which had slightly different durations (but all of them around 2 days) have been merged into one bigger offer with 2 days duration. With diffferent durations, that should not be possible? Is someone at bfx tinkering with the code and not announcing it?