There is a large extra shortcoming: debugging. When reasoning about implicit code, there are more assumptions you need to make. Debugging is basically verifying assumptions until you find the disconnect between your reasoning and code execution.
The implicit code requires you check all of the implicit assumptions. Explicit code makes checking such assumptions much easier.
Excellent point! So far I get the impression that 'level of abstraction' and it's benefits/downsides can be separated into a bunch different categories (readability, conciseness/concision, ease of getting back into things after being away, protection from various classes of errors, etc.). Ease of debugging will now be another one on my list.
The implicit code requires you check all of the implicit assumptions. Explicit code makes checking such assumptions much easier.