The argument is more complicated than that: if the Court allows the state courts and executives in WI, MI and PA to change election requirements when they will, the Constitution's delegation of authority to state legislatures to control the election process is severely weakened, and the legislature's ability to respond to changing circumstances as it sees fit (not state courts or executives) is severely compromised.
In brief, they are saying, "We, as the Texas legislature, ask you to intervene before our own courts, executive and hundreds of lawsuits weaken our ability to hold regular and stable elections."
the Constitution's delegation of authority to state legislatures to control the election process is severely weakened, Most state legislatures, if not all, have ceded the authority to appoint electors to their respective SOS and Governors. This delegation was done statutorily, by enacted laws in the various states over the past century. As it stands today, almost no state legislatures appoint the electors.