Waun Mawn -- destroyed ring cairns?

I have done posts before on the incomplete / destroyed ring cairn near Gernos Fach -- most recently following a visit by Chris and myself in 2016:

https://brian-mountainman.blogspot.co.uk/2014/05/an-undiscovered-ring-cairn-near-gernos.html

https://brian-mountainman.blogspot.co.uk/2016/08/gernos-fach-ring-cairn.html

I have had another look at it, and am still rather mystified as to why only a part of the embankment is present.  The southern part of the embankment is largely intact, and is easy to spot.  The northern segment is missing, and there are signs that it might have been deliberately destroyed -- a few subtle digs or scrapes on the ground surface........  Also, it's possible that there might have been other stones on the embankment which have been taken away. Only a couple of standing or leaning stones survive at what might have been the entrance, but there are signs of other recumbent stones embedded in the embankment.

Was this an embanked stone circle?  Maybe the archaeologists will look at it when they descend on Wain Mawn in September.

Now we have another ring cairn, which I had not noticed on previous visits.  It's right next to the hill summit on Cnwc yr Hydd, about 30 metres from the summit cairn.  It's much smaller than the Gernos Fach feature -- only about 10m in diameter.  Again, the southern part of the bank is still present, and is about 50 cm high.  The northern part of the bank is missing, and here the evidence of destruction is much easier to see -- there are hollows and cuttings littered with bedrock debris.  One cutting, in the NE flank of the cairn, is about 4m in diameter.  Could there have have been a hut here?  It does look similar to the hut circles on Foel Drygarn and Carn Ingli..........There are no signs of standing stones associated with this feature.

The Cnwc yr Hydd ring cairn -- rather a subtle feature in the landscape.  We can see the grassy area inside the embankment, and the semicircular southern section of the bank, littered with bedrock slabs and debris.  The area to left of centre is greatly disturbed, and this is where the apparent post-embankment excavations have taken place.

On this satellite image we can see the summit cairn (white dot) and the remains of the ring cairn to the SE of it.  the southern segment of the bank is clearly visible, as are the excavation hollows on the northern flank. 

Here is an hypothesis.  Might the ring cairns on Waun Mawn (there may of course be more of them, buried in the gorse bushes) date from the Bronze Age, and might the destruction date from the Iron Age?  On other hill summits, as on Carningli and Foel Drygarn (which were admittedly fortified, unlike Waun Mawn) there does seem to have been some continuity of settlement, and it would not be surprising if the later inhabitants saw earlier earthworks simply as a source of stone or building materials.......