Nintendo Co. Ltd. have reportedly applied for a patent (2020-078592) in Japan.
It seems it is intended to prevent damage to an IC tag even when the outer surface is made of a relatively soft material. This is achieved by a “reinforced area offering protection to the IC tag inside the toy”.
The reinforced area must have a hardness that is harder to bend than the IC tag therefore prevents the IC tag itself from bending. The outer material is a second material which is softer than the first material. The reinforced area is sandwiched between the cover and decorative areas.
The user then holds the bottom portion of the stuffed toy over a reader / writer or sits the bottom of the toy on the reader / writer. The tag information can then be read or rewritten.
Images from the patent illustrating this mechanism can be seen below:
It’s assumed that this patent is related to the Yarn Yoshi amiibo which was released in 2015, largely due to the original application date of March 31, 2015 for a similar patent which was rejected by the Japan Patent Office.
The filing date of this particular patent was February 25, 2020, with the application published on May 28, 2020.