Could mean they are trying to convert them into dollars again, without breaking the peg. Maybe they want to be the first to rush to the exit as they know there's most likely not enough USD backing behind tether (not 1usd:1usdt) to pay everyone back.
It seems they do have a contractual obligation of sorts. The Tether TOS state "The right to have Tether Tokens redeemed or issued is a contractual right personal to you." This language appears beginning in 2016. It is, unsurprisingly, light on the details. But the language does imply that the right exists and is non-transferrable.
Full disclosure I'm totally not versed in crypto at all, but I do recall reading something on HN a while ago that teather is audited but one of the big 5 auditors (not that it means much, look at 1MDB etc)?
