The statutory delegation, enacted over the past century at various times in the 50 states, a) specifies a method for selecting electors (either by popular vote for the whole state or by Congressional districts); and b) specifies that such electors are then appointed and certified by the SOS and the governor. It is all very clear cut - The legislative body delegating a specific function to be carried out in a specific manner to the executive body.
The current lawsuits are not contending that the delegation of responsibility for certification, etc., are unconstitutional.
The lawsuits are asserting that the state courts' and executives changing of the details, especially regarding mail-in ballots, were both unconstitutional as a matter of law, and (using a preponderance of the evidence based on eyewitness affidavits and statistics) fraudulent.