MacBook Pro (13-inch, M1, 2020) came with a 2019 charger

Not necessarily. That's just the copyright date and it's a part that can be distributed with many different Macs regardless of when the power adapter was made. They don't necessarily change the copyright date to match the manufacturing date. The copyright date is just for the revision of the power adapter. I still have an original MagSafe power adapter for my late 2007 MacBook and the copyright date is 2006.

I wouldn't worry too much about copyright dates. My mid-2012 (Unibody) MacBook Pro was made in 2014 but the bottom of the case has a 2010 copyright date that matches the initial design date for the bottom case.

Not all Apple devices are sold in the same year they are made. The dates you see are generally a model's year and a given model can be made over several years.

Likewise, the 60W charger for my Mid-2012 Unibody Macbook Pro 13-inch, made in 2013, has a copyright date affixed of 2010. I bought the computer directly from Apple and this is the original charger.

Trademarks and copyrights have nothing to do with production dates. Note the section "Duration" in this Wikipedia article on copyrights:

https://en.wikipedia.org/wiki/Copyright

You will see that most copyrights are quite long-lived, so an old copyright date is meaningful only to the intellectual properties attorneys.

If it fits and charges your Mac, you are fine.