Just dropping in to say it's feasible to get this achievement, but it's not working properly (I saw someone posting this on Reddit, tested it and worked for me). You have to desecrate 10 holy sites, but you have to pay attention to the dominant religion of the settlement. For example, if you convert as Antigonids a Cybelene settlement to Hellenic and you desecrate the holy site, it will count as desecrating an Hellenic site, even if the deity is Cybelene. For this, the religion map mode is very helpful, as you can see which is the dominant religion and the deity of the holy site. That's why people can get it either form the religion screen or the army screen.
To summarize, to get the achievement, desecrate holy sites in 10 settlements with a different dominant religion. Hope it helps!