What has changed is the codes for diagnosis, which are set by the WHO in the book International Classification of Diseases and Related Health Problems. The WHO’s ICD codes are included in DSM, basically they enable someone to be covered by their health care provider. The WHO has de-classified gender issues as a mental illness, but they still have codes that cover it, so that these people can retain access to hormones, plastic surgeries, voice coaching etc, on the NHS (or other health schemes in their countries). So while many use the DSM to enable diagnosis the WHO’s ICD codes are used for medical purposes.
The ICD was due to be updated anyway (it is always updated after a certain amount of time), the specific changes in this area were brought in due to the influence and input from various groups, such as Global Action for Trans, International Campaign Stop Trans Pathologization, WPATH, and others. The main aims of these groups were for transvestic disorder to no longer be mentioned and no association of mental illness to be made, while still retaining access to various things on the NHS (or other health care providers in their various countries). The European Parliament also put pressure on the WHO to remove gender identity diagnoses. The WHO carried out a field trial of the proposed changes then implemented various changes. So I assume these changes to the ICD codes in the DSM are what you are referring to.
The changes to the codes in practice mean that people have access to NHS funds for hormones etc, without having to be classified as having an official mental illness and down play the role transvestic disorder can play in some men’s motivations. To my knowledge there is (as yet) no changes to the descriptive text in the DSM in this area, just the IDC diagnostic codes, which are used to collect data and so people can access to NHS resources. Of course if their is a limited number of options to classify someone, e.g. no code for transvestic disorder, then any individuals that would have been classified under that code previously, would then be classified under a different code. This allows the claim that ‘no man is classified as having transvestic disorder’ even though these men clearly exist. That is one of the major problems of the changes and why particular groups pushed for certain changes.
However, I agree with the other comments here, mental health criteria is political and always has been, these changes favour the same group that has always been favoured. There is a push to make all of men’s sexual behaviours more socially acceptable, and that is usually not a good thing for women in general, these changes do just that, by making any sexual motivations invisible.