It probably wouldn't be something you consider but as a Telecommunications Consultant it is something I take notice of. After installation an OTDR test should be made on every fibre within the cable but I doubt if that is always performed. I am not blaming the fibre as the sole reason there are many but they would be outside of a discussion like this.
No the last 100m doesn't determine it at all, it is the condition of the fibres in the cable, the quality of connections and splices if applicable.