All that assumes that the putative aliens use the electromagnetic spectrum radio lengths to communicate. That may sound odd, but all we know (from Einstein to Hawking) about that stems from one 19th century self-educated man (Heaviside) who rewrote 4 of 200 field equations (the quaternions of J.C. Maxwell) into vector equations because he considered the former abominations. So there’s an awful lot we do not know by apparent and deliberate ignorance.
What exactly do the 200 quaternions say? We can only speculate as they are ignored today. However, from Maxwell came the 1859 prediction on what the rings of Saturn were made of and how they are stable; unified the theories of electricity and magnetism; advanced Kinetic gas theory; took the first color photograph; developed ways to analyze stress in a structure and even; laid the foundations of cybernetics.
Maybe our aliens are smart enough to use those field equations to communicate (among many other seemingly magical possibilities Maxwell hinted at) instantly over interstellar distances in a way we are too willfully ignorant to use or discover.
Imagine if 2/3’s of Nikola Tesla’s ideas and plans hadn’t been buried, quashed or otherwise rendered moot. Every time I read anything about him I see 3 or 4 more things he was looking at doing that somehow were shoved down the memory hole.