It's the fact that the windings are immersed in fuel. Yes, they were stout, until ethanol started eating them.
https://www.underhoodservice.com/tec...ow-technology/

Some LT1 injectors have had failure problems due to internal corrosion, which some have blamed on gasoline mixtures that contain 10% ethanol. The injector coils short out internally and cause a lean fuel condition and/or misfires in one or more cylinders. On 1996 and later OBD II models with misfire detection, this should set one or more P030X cylinder misfire codes depending on how many injectors are misbehaving.

Injector resistance can be tested with an ohmmeter, and should read 11.8 to 12.6 ohms. If the injector reads out of specs, it should be replaced.