current-time-list now defaults to nil in Emacs master

On Emacs master I recently changed the default value of 
current-time-list from t to nil as part of a transition begun in Emacs 
29, so that functions like current-time generate timestamps in the 
more-consistent and more-efficient (TICKS . HZ) form; see 
<https://bugs.gnu.org/81463>.

Although you can work around any ensuing glitches via (setq 
current-time-list t), please let me know what the glitches are.