https://www.ncbi.nlm.nih.gov/pubmed/23995658
YK11 may have additional effects that are not mediated through the AR, but it's still a SARM, in that it (selectively) modulates the AR.
It has a steroidal molecular backbone and therefore can't be classified as a SARM.
SARM's aren't classified as such by their degree of selectivity for a certain tissue(s), but by their molecular structure in concert with selectivity for specific tissues, which can vary greatly depending on the chemist's intended effects for that specific compound.
If we were able to classify compounds as SARM's based solely on their selectivity for certain tissues, we could technically classify EVERY steroid as a SARM, as all testosterone derivatives display more or less selectivity for the various bodily tissues in comparison to testosterone.
This is why some scientists refer to AAS as "SARM-like", rather than SARMs. Many steroids have been referred to as SARM-like in the literature at this point, including trenbolone, nandrolone, etc. As we all know, a drug like trenbolone is anything but selective when it comes to muscle or bone, yet it still possesses strong "SARM-like" selectivity for particular tissues (despite activating AR receptors in unwanted tissues), causing scientists to begin referring to trenbolone as "SARM-like".
When referring to the term selectivity itself, a compound does not necessarily have to possess high a high degree of selectivity for muscle tissue or bone...nor does it even need to avoid activating AR's in unwanted tissues. Rather, it simply needs to possess a higher degree of selectivity for the target tissue(s) over the majority of unwanted tissues, while having a molecular backbone dissimilar to traditional AAS. This means that we could technically classify ANY AR activating chemical as "SARM-like" depending on the researcher's developmental goals. Because of this, we don't define SARMs as SARMs simply because of their selectivity for particular tissues. Other elements need to be present, or not present. In this case, the presence of a traditional steroidal molecular structure prevents YK-11 from being classified as a "SARM" according to the term's original definition.
Many chemicals currently designated as SARMs display a high degree of activity in unwanted tissues, while simultaneously displaying a relatively low degree of activity in muscle and bone (in comparison to testosterone). S4 is a good example. Yet, they are still referred to as SARM's because they possess
some degree of selectivity for the target tissue(s) over
most non-target tissues, while having a molecular structure which differs from traditional AAS.
Any drug that possesses a classic 4 ring steroidal molecular structure cannot be classified as a SARM. However, it can still be referred to as "SARM-like".