I have been unable to find a graph showing the exact spread between 3-month treasuries and inflation over time, say in the last 20 years...

I have a data set for 3-month T bill rate and CPI. Headline CPI isn't perfect, but it will do to get the broad strokes. (bit fan of pinnacle.com)
If you simplify and assume that you reinvested each calendar quarter for three months, the real value of your portfolio over time in the last few years would look like this (after 21% corporate tax, the current rate for US corporations)
e.g., for the last decade, real portfolio value at each quarter end

2013-12-31 1000.00
2014-03-31 992.90
2014-06-30 980.06
2014-09-30 980.11
2014-12-31 987.19
2015-03-31 993.61
2015-06-30 980.70
2015-09-30 980.31
2015-12-31 982.81
2016-03-31 984.14
2016-06-30 972.01
2016-09-30 969.71
2016-12-31 968.18
2017-03-31 960.49
2017-06-30 957.65
2017-09-30 956.45
2017-12-31 953.77
2018-03-31 947.67
2018-06-30 941.14
2018-09-30 942.61
2018-12-31 947.10
2019-03-31 948.80
2019-06-30 940.98
2019-09-30 943.04
2019-12-31 944.15
2020-03-31 941.69
2020-06-30 950.16
2020-09-30 937.59
2020-12-31 936.58
2021-03-31 926.88
2021-06-30 905.57
2021-09-30 891.11
2021-12-31 877.22
2022-03-31 859.48
2022-06-30 835.16
2022-09-30 827.06
2022-12-31 822.97
2023-03-31 826.73
2023-06-30 827.72
2023-09-30 826.45
2023-12-31 835.45

To summarize: Slow loss of real value from the start of this set at end 2013 to end 2020, at a rate (inflation and tax adjusted) of -0.93%/year.
A big "sudden" loss of -10.8% in the next six months to mid 2022 (not annualized rate, just a one-time haircut)
Perfectly flat (net) since then. Down a pinch then up a pinch.

So, the celebration should be that the big sudden loss in real purchasing power in the first half of last year has ended, and the recent flat spot is at least better than when we were losing real value gradually for the ~7 years up to the pandemic. But no positive value creation.

I agree with other comments that the real value is the optionality. From time to time there is an opportunity that only someone with a big cash pile can take advantage of. Cash is the flip side of a bear market, and shares the same forgotten property: that's actually how you make most of your money, it's just that most of the time you forget that.

Jim