Not seeing much "modern" about that...looks just like all the others I've seen over the years.
Regarding stuck closed failure mode, and diaphragm ruptures...it's a tricky problem. The best seal for hot water is EPDM. But EPDM is attacked by paraffins (e.g. hot molten wax). So the diaphragm is usually a nitrile rubber, sometimes a Viton or similar. It's basically then a race as to whether the diaphragm rots away due to hydrolysis attack from hot water, or gets dissolved/softened by hot molten wax.
There are some more "modern" designs with a viton diaphragm, and a seperate rod seal or wiper of EPDM.
Oh, another failure mode is a stuck-open one, and happens when the piston is allowed to stroke a little too far, and the diaphragm inverts. Reverting the diaphragm is sometimes possible, but takes a lot more force than the return spring usually has in it. This mode is usually an infant mortality failure (one cycle), unless something else breaks or deforms first.