Because it's common for organs to be hundreds of years old, and it's common for people to want historic organs to sound as close to how they did when they were made as possible because it's uncommon for them to play in non-vocal ensemble, this leads to a relatively common situation where an organ played today may well be tuned very differently to a piano played today. Depending on the organ.
https://www.eunomios.org/contrib/francis2/francis2.pdf
Here is a second article on organs by one manufacturer tuned in 'meantone' https://www.bach-cantatas.com/Topics/Meantone.htm. It's also the case that harpsichords were commonly tuned in meantone https://www.harpsichord.org.uk/wp-content/uploads/2015/04/te... which might actually support the claim that historic non-organ keyboards sounded different from organ keyboards (specifically, if Bach didn't like the mean-tone organs he played and it was common to tune harpsichords in meantone, that would seem to provide some evidence for both temperaments existing and sounding different on the different types of instrument in the same historic period).