There is a huge difference. One comes from peoples savings, one comes from the fed.
However, the savings and investments of people into Stablecoins is going to be nowhere near the level of the fed. In March - June, the fed printed 2.2 trillion.
Likely Stablecoins will take a decade or more to reach that level.
Banks will be buying treasuries for the stablecoins issuing. Just another way for the gov to stimulate tbills and note markets without the fed.
But it can only last so long, eventually there is nowhere near the money in the system needed at lower rates to continue. Enter the fed.