I haven’t personally seen anyone so far who is a native Sanskrit speaker(in all the states that I have visited). All of them learn it as a second language. You probably can’t even call that as a second language, because they generally don’t use it out of academia. So yes, endangered.
That said, reportedly there are at least a couple of villages in India where people still speak Sanskrit - *only* Sanskrit. Most notable of them is Muttoor in Karnataka. So technically the website might be correct.