There are a few issues at hand concerning words such as begin, start, end and finish.
These are time delineation terms, or temporal boundaries.
Some languages that do not have tense inflection, use these words to define the tense of a predicate. Their use would naturally coincide and overlap with grammatical tense inflection.
2ndly, finishing a building is a construction term. Finishing could include painting, stucco, siding, trimming, etc.
Finishing could also include a lengthy administrative process of inspecting, qualifying and certifying the fitness of a building or structure.
3rdly, even if finishing is a momentary event, as far as humans are concerned, finishing still takes more than 5 seconds.
- I will finish eating at 5 pm tomorrow. At 5 pm, I will have the motivation to finish my eating.
- I will have finished eating at 5:15 pm tomorrow. At 5:15 pm, I would no longer have the motivation or the necessity for the motivation to finish eating, because I will have finished eating.