Keep in mind that this statment is under the section "8.6 Use of Plots". The reason this statment was included is based on the same view as any other inspection tooling.
Per the referanced specification D1-8110-9 there is a requirement to account for temperature and humidity in the creation and use of plots
"Development and validation of PDTs will be done in an environmentally controlled area using a real time monitoring system for temperature and relative humidity."
This concept of monitoring temperature and humidity is also addressed in section 5.3 of ISO 17025