The sibling comment's linked article answers this.
"If you put money in a checking account, regulators make banks set aside a cushion as reserves in case they get into trouble. But if you put money into a savings account, regulators tell banks they don’t have to reserve anything. The catch is that it’s only considered a savings account if the consumer is allowed to make no more than six withdrawals per month.
It’s worked that way for years.
But then Covid hit, and regulators realized that having trillions of dollars in savings accounts with limited withdrawals was a burden as 22 million people lost their jobs.
So last April the Fed changed the rules and eliminated the six-withdrawal limit on savings accounts. It wrote:
The interim final rule allows depository institutions immediately to suspend enforcement of the six transfer limit and to allow their customers to make an unlimited number of convenient transfers and withdrawals from their savings deposits at a time when financial events associated with the coronavirus pandemic have made such access more urgent.
It was an obvious and nearly risk-free way to help people. Just let them have easier access to their savings.
But it changed the relationship between M1 and M2.
Savings accounts are measured in M2 and left out of M1. But once the six-withdrawal rule was removed, every savings account suddenly became, in the eyes of regulators and people who make these charts, a checking account.
So M1 exploded higher. Not because the Fed printed a bunch of money, but because trillions of dollars in savings accounts were reclassified as checking accounts."
https://collabfund.com/blog/the-fed-isnt-printing-as-much-mo...