It's not that simple.
Key is 'was' =eimi / nv = verb, imperfect, active, indicative, third person, singular.
verb — A word that describes an action, state of being, or the production of a result.
imperfect — The verb tense where the writer portrays an action in process or a state of being that is occurring in the past with no assessment of the action’s completion.
active — The grammatical voice that signifies that the subject is performing the verbal action or is in the state described by the verb.
indicative — The mood in which the action of the verb or the state of being it describes is presented by the writer as real.
third person — In grammar, “person” refers to the feature of verbs or pronouns that helps us distinguish
singular — Refers to one person or thing.
Seems the author is conveying absolute existence.
Also note eimi is Imperfect Active Indicative
"We were eating" in the following sentence would be expressed using the imperfect in Hellenistic Greek.
Imperfect Active Indicative
We were eating dinner when my sister arrived. "Were' Imperfect Active Indicative. In the beginning was the Word. Was =Imperfect Active Indicative.
the primary function of the imperfect tense is to convey imperfective (progressive) verbal aspect in narrative past-time contexts
imperfect Tense
The imperfect tense shows continuous or linear type of action just like the present tense. It always indicates an action continually or repeatedly happening in past time. It portrays the action as going on for some extended period of time in the past.
John is stating = at that millisecond when the beginning commenced Jesus was already existing.