It appears the reason for amendment is not stated in the F6 Post-Effective document, but the reason must be given upon request (see below):
"Notice of any amendment to the Deposit Agreement or form of Receipts shall not need to describe in detail the specific amendments effectuated thereby, and failure to describe the specific amendments in any such notice shall not render such notice invalid, provided, however, that, in each such case, the notice given to the Owners identifies a means for Owners to retrieve or receive the text of such amendment (i.e., upon retrieval from the U.S. Securities and Exchange Commission's, the Depositary's or the Company's website or upon request from the Depositary)."
(D) Definition of Fundamental Change. A “fundamental change” will be deemed to have occurred upon the occurrence of any of the following:
(i)(1) the consolidation or merger of the Corporation with or into any other person (other than any merger primarily for the purpose of changing the Corporation’s jurisdiction of incorporation and resulting in a reclassification, conversion or exchange of outstanding common stock solely into common stock of the surviving entity) or (2) the sale, lease or transfer, in one or a series of related transactions, of all or substantially all of the Corporation’s assets (determined on a consolidated basis) to any person or group (as such term is used in Section 13(d)(3) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”)) other than a sale, lease or transfer to the Corporation or any of its subsidiaries;
When is a post-effective amendment (as opposed to a prospectus supplement) required to be filed?
The three instances when a post-effective amendment is required instead of a prospectus supplement are when:
there is a “fundamental change” (a greater threshold than “material”) to the disclosure;
disclosure in the registration statement must be updated for Securities Act Section 10(a)(3) purposes; and
there is a change to the plan of distribution (e.g., switching to an “at-the-market” offering from a firm commitment offering).