IDK if I believe that number of congregations is that indicative of anything.
In my experience, all churches in decline, sooner or later, start closing down congregations. I’ve seen it with the Mormons, Church of Scotland, Unitarians, Swedenborgians, Christadelphains, Methodists, Episcopalians, Christian Scientists, Brethren, Baptists, and others. If JWs do experience decline then it will show up in the number of congregations over the medium to long term. In the past few years the number of congregations have declined in line with a stated policy of consolidating resources. If the number of congregations continues to decline then I would say it indicates real decline regardless of what the others figures such as publishers or baptisms are doing. On the other hand, if the number of congregations goes up then it probably confirms growth in general.