AFAIK, It has always been the case for many decades, when the yield of treasury bond rise, it will send the high growth stock down for obvious reason. But The Yellen statement above is about “borrowing limit” thatthe US government are allowed to borrow, nothing to do with the yield of treasury bond.
When there is greater uncertainty regarding the borrower fulfilling its payment of a bond, the yield of the bond rises (ie. Generally, less safe = higher yields) and the market value of the bond falls.
But when come to the yield on U.S. Treasury Bond, it is the US government department responsible for issuing all Treasury bonds who will be making that decision. They will need to announce this in public.
It depends only on the agreement of both parties, to authorize the rise of debt ceiling. US Treasury Department only do what is allowed by their mandate (decisions made by political parties).
Both parties can take long to reach an agreement, usually they reach an agreement in the last minute. One of the last US major debt event (Obama administration, 2013), it took several weeks, the US public services were closed, and the civil servants went home without pay, only essential public services remained opened.