I haven't heard or seen this stuff on tracking "plus" yet... thanks for the info.
I agree, it's not worth having an extended tracking number history for our situation... we know whether it got there or not in a few days and don't need long-standing records. Or if you do, just take a picture of the tracking number/receipt and keep it on your phone... you just have to know the number to get inquiries from USPS.

FWIW, the USPS website still shows details for First Class mail that include large envelopes with a weight limit of 13 oz... they can be rigid/non-machinable for a small additional fee. I guess I'll keep doing that until somebody at USPS says I can't.

Here's the link:
https://www.usps.com/ship/first-class-mail.htm