It appears an unidentifiable Apps Script project creation via Apps Script API usage quota exists and has been reached on my end (i.e. the IAM & admin console indicates all API usage is well below its limits).
The resource limit appears unspecified here as well: https://developers.google.com/apps-script/guides/services/quotas.
Error resulted from implementing getContent and create methods. At the time, there may have been roughly 100 calls (this was done in testing). From additional runs, the error appears to have resulted from an unspecified usage period limit (24 hours?).
A quota increase is desired, but without it being apparently listed in the IAM & admin console, it is difficult to identify how this could be done.
As per above, what is the imposed limit or how may it be otherwise identified, and how may it then be increased (if possible)?
Google does not disclose all of the rates that they limit, likely to prevent circumvention or to allow greater fluidity in enforcement.