First of all, the page itself just correctly warns that orcas can't just be freed. It's not like we should go ahead and literally dump them into the ocean and abandon them. No one is advocating for this. Doing this generally with most types of animals still causes all kinds of problems (see for example https://www.cnn.com/2002/TECH/science/07/23/snakehead.poison/index.html )

On the flip side, when a well prepared effort is launched, captive orcas have survived in the wild successfully. See https://killerwhales.fandom.com/wiki/Vasilievna for a good example - and this is what folks are pushing for.

Finally, I have some concerns about the source itself. From https://www.sourcewatch.org/index.php/Environmental/_Literacy/_Council it seems that enviroliteracy.org is part of the George C. Marshall Institute.

In case you don't know much about that institute, here's the most important bits:

The George C. Marshall Institute (GMI) is a "non-profit" organization funded by the profits from oil and gas interests and right-wing funders (listed later). It has received substantial funding from Exxon's Exxon Education Foundation.
Its nominal creators, aside from Exxon-related entities and others, were William Nierenberg, Frederick Seitz and Robert Jastrow. This industry and right-wing front group

https://www.sourcewatch.org/index.php?title=George%5C_C.%5C_Marshall%5C_Institute