The grammatical explanation to English simple past tense contains the information about the formal features and functions of simple past tense but not the emphasis on the guideline “Do not rely on the temporal adverb to understand when the action takes place”. The grammatical explanation just like this:

The past simple tense is one of the tenses used to talk about events in the past. It refers to finished actions and events. Very often the English past simple tense ends in -ed.

Following grammatical explanation, there are two kinds of activities: mechanical activities where students are asked to transfer the present tense forms into past tense forms or substitute the past for the present; meaningful activities where students are more likely to be trained in selecting correct forms of the given verbs based on the information provided by context, particularly on the temporal adverbs yesterday, last night and so forth.

Benati, A. G., & Lee, J. F. (2008). Grammar Acquisition and Processing Instruction: Secondary and Cumulative Effects (pp. 99-106). Bristol; Buffalo: Multilingual Matters.