I guess the GPLv3 has provisions for patents, but older licenses didn't. I remember some controversy around open source video codecs that you were not able to use safely because they were infringing patents.
GPLv2 didn't have a patent grant because it wasn't a very well-known issue in 1991. Apache 2.0 was the first free software license to have a patent grant (which unfortunately made it GPLv2 incompatible) but GPLv3 included a similar (though stronger) patent grant because of Apache 2.0.
While these may sound like theoretical problems, people have been sued over using GIF, MP3, etc before. Every time you install Firefox, it will download a free software binary from a Cisco server that does h264 decoding[5]. However, they cannot legally recompile the binaries themselves as it means that the patent grant no longer applies and Mozilla (or your distribution) could be sued -- even though the binary's source is BSD-licensed.
[1]: https://www.gnu.org/philosophy/fighting-software-patents.htm... [2]: https://www.gnu.org/philosophy/danger-of-software-patents.ht... [3]: https://www.fsf.org/licensing/h264-patent-license [4]: https://www.iis.fraunhofer.de/en/ff/amm/prod/audiocodec/audi... [5]: http://www.openh264.org/index.html
I can understand why Facebook would want to have a clause like this (to discourage lawsuits against them), but I would consider it against the spirit of open source to do so (ie. Facebook should be able to continue to do this, but I wouldn't consider React to be open source software in that case).