Unless you're literally buying government bonds (that are yielding very low and sometimes negative returns) your savings will still translate to increased spending elsewhere.
https://fred.stlouisfed.org/series/EXCSRESNS
The Fed even pays a small amount of interest. IOER is currently 0.1%
Does anyone understand the exact point being made?
The "liquidity constraints" discussed in the abstract may be one such friction, but it's quite common for agents to be liquidity-constrained or unwilling to incur debt even irrespective of any negative supply-shock, so it's not quite clear to me what points the paper is trying to make.