The question asks for the false statement. Free cooling is a highly mature, proven, and widely adopted technology in the data center industry for improving energy efficiency. It leverages low external ambient temperatures (air or water) to cool the facility, significantly reducing or eliminating the need for mechanical refrigeration. Therefore, the statement that the technology is not mature and should be used with caution is definitively false. The other options correctly describe the well-established advantages and principles of free cooling solutions.

B. Free cooling is widely implemented globally in various forms (e.g., air-side/water-side economizers), making this statement true.

C. This statement accurately describes the core principle of free cooling, which is its primary advantage for achieving low Power Usage Effectiveness (PUE).

D. This statement is correct; the effectiveness of free cooling is directly dependent on favorable seasonal temperature differences.

- Huawei Smart Data Center Facility Solution Overview, "Cooling" section. This document presents free cooling as a key, mature component of its energy-saving solutions, contradicting the idea that it is not mature.

- ASHRAE TC 9.9, "2021 Gaseous and Particulate Contamination Guidelines for Data Centers," provides extensive data and best practices for implementing air-side economization (a form of free cooling), demonstrating its maturity and acceptance.