Are any of the special commemorative coins issued by the Mint "coins"? Yes, they are. One term for them is "Non Circulating Legal Tender". Are they "collectable"? That is for each person to decide.
For those of us old enough to remember a time before the Mint made bullion coins, we recall the heavy lobbying that occurred to get the Mint to issue bullion, and the sponsors of that legislation were adamant that the coins have legal tender status (a face value).
I see bullion as a means of trade or of storing value/wealth. If it is issued by a government and has legal tender status, especially if it has a face value, then it is a coin in my opinion. There are lots of gray areas, however. Consider the Maria Teresa taler dated 1780 - still minted by Austria, no stated face value and no legal tender status in the issuing country in modern times (as far as I know), but it is condsidered a coin.
Whether or not a coin is "worthy" of collecting is a matter of personal opinion, but the fact remains that Silver Eagles are widely owned as money/investment/wealth, and they are collected.
P.S. - if circulation is the defining criteria of a coin, then do obsolete coins stop being coins when they stop circulating? Are Morgan dollars no longer coins because they no longer circulate?