If it didn't have the grill flaps then corrupt data is probably right.
There is always data being sent to the ECU and some will be corrupt. Sometimes with a coolant sensor this can be from a tiny air pocket or the sensor taking too long to respond ... these variances are thrown out by the ECU and a previously known good value is used. Basically the ECU sees temp in real time but uses the average most of the time.
There is an amount of data that can be thrown out before the ECU throws a code. I'm not sure what that limit is but odds are if the limit is too low there will be a calibration update available once enough customers have the problem and a new coolant temp sensor does not fix the issue.
OH, you're not playing dumb ...