No, not at all. Let’s look at what these things are, then look at the people who use Si and Ni Myers-Briggs functions.
Situational Memory
According to What is Situational Memory?, situational memory is a condition in which a person has to be in a certain environment in order to remember information.
Situational memory sometimes called “Environmental context-dependent memory” refers to an ability to remember information when in one situation that you are unable to remember in another.
All of us may experience that from time to time but everyone with normal mentality is able to remember things that are not in the immediate environment. Si and Ni merely refer to the preference of some individuals to use those functions (Si and Ni) to absorb information.
Conceptual Memory
Concerning conceptual memory, here is a quote from Conceptual short term memory:
When one perceives a meaningful stimulus such as a word, picture, or object, it is rapidly identified and in turn activates associated information from long term memory.
Again, this describe the experience of humans in general.
The functions of Myers-Briggs Personality Type all describe normal human psychology. None of them are abnormal. Some of them are more common than others.
Si Types
Si is extremely common, given that it is the auxiliary function for two of the largest MBTI groups: ESTJ and ESFJ. In addition, it is the dominant function of two fairly large introvert groups: ISTJ and ISFJ.
The strength of these four groups is focus on detail and routine. I admire them for their ability to do the dishes, laundry, windows, lawn and countless other routine tasks that drive me crazy before the first hour is up. I admire that they are able to do this day in and day out, year after year. Many of them stock shelves, keep the books, build our streets, re-shingle our roofs, landscape our grounds, maintain our buildings, deliver our mail, police our cities, nurse our sick, the list goes on and on and on. This has nothing to do with situational memory as described above.
Si Described
The quote below from 10 Signs That You Might Be an Introverted Sensor – Psychology Junkie may be helpful in answering the OP. My guess from reading the autobiographical part of the article is that the writer is ISFJ, though I cannot confirm this.
Introverted sensing is a perceiving (information-gathering) function. It focuses on the subjective, internal world of personal experience and compares and contrasts new experiences to past experiences and memories. Si-users tend to notice patterns repeating themselves and are quick to spot changes or inconsistencies in their environment. They trust personal experience and subjectively explore the impact of current events, choices, and consequences.
Ni Types
Ni is far less common than Si, but a lot of people prefer using it. Most use Ni as auxiliary function: ENTJ and ENFJ. Introverts are fewer in number across the board; the Ni dominant types are: INTJ and INFJ.
Ni are the great inventors of the world, along with the other iNtuitives. You may find the older ones in supervisory positions among the Si masses, but they somehow survived the boredom of the lower ranks to get there, possibly solving problems and learning the ropes (of the industry/company beyond their immediate responsibility) as a way to stimulate their brains along the way. Their strength is visualizing the larger (global) picture of the situation in all its parts and how they fit together. For example, when I move to a new place, I don’t feel comfortable until I know how the entire system of the organization works from maintenance to landlords and CEOs. This has nothing to do with “conceptual memory” as described above.
How Ni Works
I’ve been reading Dr. Drenth’s Personality Junkie for years and respect his take on things; I think he is INTP. Here is a quote from Introverted Intuition (Ni): An Inside Look | Personality Junkie
What seems to be occurring is that many INJs have a highly sensitive inferior function, Extraverted Sensation (Se), which gathers copious amounts of sensory information from the outside world, including subtleties that other personality types tend to miss. Their Ni then subconsciously processes this data in order to make sense of it, like assembling pieces of a puzzle. Once finished, Ni generates an impression that seems to come out of “nowhere.” But the fact is that the intuition did not come out of nowhere, but from a synthesis of sensory data gathered from the immediate environment combined with information from the INJ’s own psyche.
Life Lenses 