Why is market absorption of issued US Treasury Bonds (with the Fed purchase plan) a problem? Financial market reports suggest that there are uncertainties about the Federal Reserve's ability to absorb new US Treasury Bonds issued in larger quantities to support the US government's growing budgetary requirements (i.e. the pandemic support of the economy).
This hypothesis is bolstered by the example of 2018:

...real yields rose and stocks and corporate bonds got clobbered until
the FED reversed its tapering exercise and started buying USTs in
size.

Questions:

Why can't the Treasury and the Federal Reserve agree upon a
controlled issuance and instant procurement of UST bonds &quot;straight
from the printing press&quot;?
Why subject the market to the ambiguity of
being able to partake in this exercise, which is specifically aimed at funding
the budget through the Fed's resources?
Why can't the Treasury and the Federal Reserve agree upon a controlled issuance and instant procurement of UST bonds &quot;straight from the printing press&quot;?

Treasury bonds are not “printed” at a “printing press,” the only “printing press” is run by the U.S. Mint, where they print Federal Reserve Notes (e.g., dollar bills). Treasury Bonds/Notes/Bills are sold at auction.
Not sure of the exact statute that forces this, but the Federal Reserve does not bid at auction, they buy in the secondary market. This answers your question.
Update: a FAQ on the Fed website: link.

Why subject the market to the ambiguity ...

Because there is no legal alternative, other than changing Fed operating procedures to having them cap bond yields. (One can search for discussions of “yield curve control” for more details.)
As for financial market commentary, it is not always reliable, so statements made there need to be taken with a large grain of salt.