Cold hardy does not mean freeze proof. It really depends on just how cold did your overnight lows get?
In general these early spring crops do better getting through cold snaps moist rather then dry!
If your spinach went through 28 degrees moist compared to 26 degrees dry, that could make a huge difference. It's really hard to say. Just how cold did it get by you?
Look at me here in Michigan, I had 26 degrees. I never saw any damage to Hostas before in the 50+ years that I have grown them yet I had minor leaf damage at 26. Spring time damage was something I had never experienced before.
But like I said, soil moisture makes a difference, wind makes a difference, cloud cover makes a difference.
Look I bought a couple of new rose bushes last Friday from a local nursery. They both had leaf damage. They were each trimmed slightly. This was probably cold damage. Normally a nursery would cover sensitive plants but how can you cover plants in a 3 acre nursery. They are in fact colder then me in Livonia MI. They are in Canton MI which had parts of it hit 23-24 degrees.
All I am saying is that cold damage can be very spotty. But in the spring, tender shoots can have a tough time with temperatures below freezing whether its 24, 26 or 30!