No this has been on v17 since I moved from Vbox about six months ago.  I do agree that's what's going on.  I will also note that I'm using the firmware TPM built into my Ryzen CPU.  Upgrading the bios also breaks bitlocker on the host OS volume after a BIOS update.  I work around that by suspending bitlocker on the OS volume, updating the BIOS, and then it auto resumes bitlocker on reboot.  This is a custom built system with an Asus motherboard.  I'm going to leave the vTPM off the guests so this doesn't happen again.  In theory, I should be able to keep the vTPM but would need to remove it before updating BIOS and then add it back after the update.