While the download itself is "only," 20GB, because Titanfall comes with every single language of the game - which at the moment, you must install - the final install base is 50GB, some 35GB more than the Xbox One version.
Respawn has yet to release a good reason for this, but it was initially thought by some Reddit users to be because of EA's Origin limitations. However that has now been disproved.
Of course there's big calls from the community asking Respawn and EA to figure out a way to make the language selectable before downloading, thereby bypassing the need to not only download the gigabytes of extra audio, butt to install them. Massive downloads a pain for those that live in remote areas or those with data caps, and the install size makes it hard for those with SSDs to take advantage of their boosted load times.
It might also be interesting to note if ISPs have anything to say about this, since ultimately they're the ones paying for these huge downloads, even if their customers are paying for huge uncapped packages.