That actually looks lika a problem I've been dealing with myself, today.
In my case it was with Octanes Subdivision feature (and "marked sharp edges").
The Subdiv modifier in Blender doesn't create that kind of artifacts on it's own (it doesn't "split the mesh"), but it could happen if you have the Edge Split modifier before the Subdiv.
If you want sharp edges with Subdiv modifier (Or Octanes Subdiv) you can use the "Edge Crease" tool in Edit mode (Shift+E and drag/type in value or via the Edge menu [Ctrl+E]), and/or add more supporting edge loops (perhaps not suitable in this case..), sometimes you might need to increase the edge crease on some connecting edges as well to get it to look right though..
Windows 10 Pro - AMD Ryzen 7 2100X 8 core 3.70GHz - 32GB RAM - GeForce GTX 1080 8GB
Stand Alone + Blender Plugin user