Why the F-Droid repository doesn't show latest version of Firefox to download? The latest version of Firefox available for download is v50.0 but on Play Store v52.0 is available.. Why F-droid doesn't show latest version?

Firefox (Browse the web) - https://f-droid.org/app/org.mozilla.firefox

https://f-droid.org/wiki/page/org.mozilla.firefox
F-Droid doesn't include Firefox anymore (*) but some builds from Firefox code, such as Fennec and Icecat.

(*) It is due some privacy concerns, Tracking, UpstreamNonFree and Non-free Addons

At the moment
Icecat 52.4.1

Fennec 56.0
Version code: 560020,560010,560000 
Current scheme: XYZAR, where X.Y.Z is upstream version, A is architecture (0 = ARMv7, 1 = x86, 2 = ARMv8), R is revision (if we need to re-release)