I did say it was an approximation. But if you're going to be pedantic:
I've found zero decrease in the use of Line 21 CC. Trust me, it is heavily used in my household, we would notice.
Also, the issue is not that EIA-708 isn't embedded in the image, it's that modern HD wiring does not support closed captions. You can't send EIA-608/Line 21 captions over HDMI, and component cabling ONLY works if it is 480i.
So while there are usually 2 different format caption streams for TV programs, the issue is that the device playing the program must now decode it and display it because you cannot send it to the TV's captioning decoder.
A raw recorded transport stream will still contain the stream with the EIA-708 AND the embedded EIA-608, but unless you are willing to watch that program in standard definition, the DVR must decode and display the captions.
Apparently the VRX, like a few other units has decided to extract the captions (probably 708) and save it in a custom format. As long as it isn't re-encoding the video, the 608 should still be present as well.
Some custom formats can be converted with software solutions if you have the need. No telling what the VRX's format is, it could be plain text for all we know.
I put it to you that if the VRX has an older RF or composite output, that it will show line 21 captions on playback.