While the phrase "nothing is implicit" was used, there actually are so-called "implicit inputs" in Guix. :-P Each package uses a certain "build system" which can be e.g. "gnu" which has e.g. autotools and bash as "implicit inputs" so every package using that build system gets those dependencies.
Do you do psuedo packages, like the Debian model of the build-essential package which pulls in a standard cloud of normal stuff, no need to list libc6-dev by name because that's a dependency of build-essential, but if you want libpcap-dev you need to pull it in specifically by name because its not in build-essential?