Difficult to say what the SAMS are actually hitting - pretty standard for the USAF/USN/USMC to use "bait" to stimulate the air defenses and make them focus on cheap drones/cruise systems, which makes the SAM systems engage unimportant targets, waste ammunition on them, as well as helps overwhelm the human element in the kill chain. So, while it's certainly possible that the newer stuff like the S300 and S400 variants in Syria, and other newer Buk systems, can perhaps take out the "new and smart" (haha) cruise missiles in certain parts of their flight profile, IMO it's more likely that the intercepts caught on video are mostly the SAM systems taking out targets that were sent to be taken out by SAMS intentionally.
The SAMS can also be command detonated, at least the S300/400 can, and some of the explosions in the sky can be the system or operator doing that for various reasons.
edit - most of the explosions/possible intercepts I've seen video of look to be at 2000ft AGL or even higher. Low altitude is still something that even stealthy cruise missiles will probably be taking advantage of, which makes me think that the stuff up higher (not NOE) is even more likely to be bait intentionally placed there.
edit2 - detailed briefing on the platforms and missiles used, and the general giving it claims no missiles were intercepted by Syrian defenses.
Combination of JASSM, Tomahawk, Scalp, and Storm Shadow missiles from the USN, USAF, RAF and French Air Force. USS Monterey(Tico class), USS Laboon(Burke), USS Higgens(Burke), Languedoc (French Navy/Scalp), USS John Warner (Virginia class, two B1B, Tornado/Typhoon, Rafale/Mirage. No friendly losses reported, and again, claims that all missiles reached their targets. Also stated was Syria fired over 40 SAMS, and most were fired after the last incoming cruise missile had already reached its target.
