Some more Googling leads me to this British site:
Here’s a soup spoon, 8" long. Note shape of bowl.
Here are serving spoons, also 8" long.
Here’s an entire 8-piece set, including cake fork and fish fork. That large spoon there is what I’d call a tablespoon, but they’re obviously calling a soup spoon.
Looking at that Replacements site:
On this page is listed a “place spoon”. It notes that many people call these “tablespoons”, and that’s what I’d call it as well. The next page has a “tablespoon”, which they note is used for serving vegetables; this is what I’d call a “serving spoon”. The “teaspoon” is smaller than either of these, and it’s pretty much as described on the first page. A “soup spoon” is what I’d call the “bouillon”, “cream soup”, or “gumbo” spoons.
I think the trouble is that today’s flatware categories are too simplified to account accurately for the bewildering variety of silverware that they had in the 19th century.
Nowadays, according to Miss Manners, the standard “tablespoon” or “place spoon” of the typical commercial flatware place setting is correct for all soups and spooned desserts, plus morning cereal as well. As acsenray notes, a teaspoon is not standard for those purposes and is used only for stirring coffee or tea (although if you personally prefer to eat soup or stew or cereal with a teaspoon, I’m certainly not going to argue with you).
But back in the day, things were different. As has been pointed out, there were different types of spoons intended for different types of soup. According to this flatware identification guide, bouillon spoons, cream soup spoons, and gumbo spoons are all round-bowled spoons of different sizes. (That Replacements site actually describes them all as round-bowled, but the accompanying visuals are a little misleading.)
You can see actual photographs of soup spoon varieties including all the round spoons, along with an “Oval Soup Spoon” (which I bet is what the OP’s friends have) and a standard “Place Spoon” (somewhat smaller).
My guess is that the large oval soup spoons like the ones the OP is talking about were the standard soup spoons for clear soups (not bouillon served in bouillon cups with small round-bowled bouillon spoons, though). As time passed, their soup-eating function was assimilated by the slightly smaller, more versatile “place spoon” (now also called a “tablespoon” to confuse the British, who think a “tablespoon” is a serving spoon and a “soup spoon” is a place spoon).
However, some people still considered it classy or fun to have the old-fashioned large oval soup spoons, even if they had to get ones in a different pattern from the rest of their flatware. My mother still has a few “big soup spoons” left over from my grandmother’s silverware.
I think the major lesson to be learned here is that flatware technical terminology is desperately in need of standardization.
Wow. That list of flatware is intimidating, isn’t it.
I am still grumpy about my nonexistent large soup spoons, I think.
(Not in the face! Not in the face!)
Brit here …
In the UK the typical, everyday place setting will be a knife, fork, teaspoon, dessert spoon, shovel and chopsticks (OK, I lied about the last two).
A teaspoon is only used for adding sugar to / stirring drinks or taking medicine.
A dessert spoon holds 2 teaspoons, and is used for desserts / cereal / soup (unless, like me, you have round-bowled soup spoons for show).
A tablespoon holds 4 teaspoons and is used solely for serving.
A serving spoon is a large tablespoon.
Hope this helps. 
Or perhaps it’s for eating qagh…
I like rusty spoons …
All right. Now I can’t live without a set of Klingon teaspoons.
Shrinking Violet , can you say anything about soup spoons?