I would not agree that attractivity is the only difference. Gravel, having sharply cut / crushed edges, is much more likely to be stable as sharp edges will lock on one another (at least partially - in case of very loose gravel), while smooth edges of pebbles are much more slippery and loose. Try riding a bicycle on each and you’ll see what I mean. One is uncomfortable, other is suicidal.
Also, pebble beaches (to which you link) are my favourite (don’t like sandy ones as sand gets into everything!), and crushed gravel ones with sharp edges would definitely be amongst the most horrible ones (probably tied for worst position only with freshly laid smelly half-melted-from-the-summer-sun tarmac beach 
).
So I absolutely do not agree that something which is the best should be marked as a duplicate of something which is the worst.
Additionaly in common language gravel is used for all kinds of loose stone material notwithstanding if it is rounded or sharp edged.
OSM tags are not “common language”. We’ve had clearly defined surface=pebblestone for more than a decade: “Pebbles are stones rounded by waves or river flow”. So if it is made only of pebbles, then it is surface=pebblestone. If it is not, then search for another, better matching value of surface=*.
@Map_HeRo if you think that surface=gravel is confusing, and thus should better be deprecated and replaced by several more fine-grained (excuse the pun) tags, that I would agree with (although I personally probably would not volunteer to dedicate the rest of life to pursuing that holly crusade).
However, suggesting that we should deprecate several well-defined tags (like surface=pebblestone) and replace them with one unclear and fuzzy tag representing all of them (like surface=gravel), I definitely do not agree with in the least.