No. Apparently not. The relevance of Past perfect lies in the fact that it differentiates between the time frame of two events, when both of them happened in the past.
Example:
Before she left for her college, she had finished her lunch.
You can use After too. In the given sentence in your question,
Mario had already arrived home when his mother walked in.
it is understandable that Mario had reached home before his mother walked in.
BUT a simple,
Mario had arrived home.
is meaningless and unnecessary as you are not referencing before what event had he arrive home. You can use simple past here. Of course, if in a conversation it is relevant that you did it before some action you can use simple perfect like you cited. Like:
2nd friend: Where do you work now?
1st friend: I work in ABC company now-a-days.
2nd friend: Oh! I see. I had worked there. (It means he had worked there before he left that job)
So put it simply,
Past perfect is not used unless and until we are comparing the time frames between two events. You can read more on past perfect in English Page: Past Perfect Tense.
This "authority" is in error; the past perfect is not necessarily required here, although there are circumstances in which it would be preferred in formal discourse, and the simple past is not incorrect, although there are circumstances in which its use would be deprecated in formal discourse.
This is in the first instance a matter of context— specifically, what you are trying to express and what time you are talking about, what grammarians call Reference Time.
Perfect constructions do not express events prior to Reference Time; they express a state grounded in prior events which obtains at Reference Time. So if you are talking about a time in the past when your subject's previous unfamiliarity with bears was of immediate relevance, the past perfect will be appropriate:
As she was hiking in the Tongass National Forest she was suddenly confronted by a menacing dark creature her own height and twice her mass. She did not recognize it—she had never seen a bear before she moved to Alaska.
But if your Reference Time, the time you are speaking about, lies before the time at which she moved to Alaska, a past perfect will not be appropriate:
She was in her youth a keen student of wildlife—kangaroos, wallaby, emus—but she never visited zoos, which depressed her, so she never saw a bear before she moved to Alaska.
In less cut-and-dried circumstances, usage varies: formal usage and British colloquial usage tends to employ the past perfect more often than US colloqual usage. If you have an appetite for technical grammar, I modestly recommend our Canonical Post on Perfect Constructions, particularly sections 3.2 and 4. If not, the best 'rule of thumb' respecting use of the past perfect is FumbleFingers‘ Perfect Truism:
”Don’t use the perfect unless you need it.”
Best Answer
Instinctively, I would prefer option 1. But it seems the canonical post cited by user 170849, and written by Stoney.B suggests that either option is acceptable.
4. How and when should I use the perfect?
OR
N.B. Where the original is not in bold, I have stated as [emphasis mine]
In the OP's example; the event (rain) specifically occurred prior to an occurrence (a muddy road). The road was muddy due to a rainfall that happened and ended at a very specific point in time: the day before. Some might name the phrase in bold an adverbial phrase or an adjunct, regardless, this phrase/adjunct unequivocally establishes the sequence of events, and in a narrative setting, the Past Perfect is preferable in this instance (especially under English exam conditions!).