time machine message: "backing up encrypted drive to an unencrypted drive" (NOT!)

I have a brand new 13" MB Pro of the model upgrade just announced about July 9th. It is running Mojave 10.14.6 and has a 1 TB drive. I migrated my apps, data & settings from an 8 yr. old 15" MB Pro running High Sierra. My new machine has about 620 GB of disc contents. Everything went absolutely fine and smooth with the migration and setup. NONE of my drives or data has EVER been encrypted. I have never turned on "File Vault." I have never chosen to encrypt any of my Time Machine backups.

Due to the OS change large hardware difference and the fact that Time Capsule backups had been getting excruciatingly slow, I decided to abandon my Time Capsule (no longer using as wi-fi source or router anyway) and start backing up to a new, 2 TB Seagate USB SSD. After formatting the new drive on my Mac, I set up Time Machine and manually started my first backup.

As the Time Machine backup started, I got a message of notice: "You are backing up an encrypted drive to an unencrypted drive."

As I said, nothing has EVER been encrypted in my system, nor did I choose to encrypt the drive on the new MBP. Checking settings verifies that File Vault is turned off. As I write, the backup seems to be progressing quite nicely and I appear to have about half the 630 GB backed up in just a bit over 90 minutes (roughly 20 times faster than my old Time Capsule used to backup on my old MBP!).

So, do I have a problem? Is this error or warning message of any significance? Why would Time Machine mistake my new machine's unencrypted SSD for an encrypted drive?

Since this is my very first backup, I do not want to interrupt it to see if the problem recurs, but I will of course test for it once I have a secure backup. But I thought I'd put this question out there to see if anyone knows if I should be watching for something??