OK, '640mm effective' or '640mm equivalent' are bad nomenclature.
The problem is that in the past there was only 35mm, so focal lengths were usually used instead of angle of view.
And the tradition has gone on of quoting an equivalent focal length for small sensor lenses, because it is easier for people to compare different cameras by using the 'equivalent' focal length - People have a good feel of what to expect from a 200mm lens compared to a 28mm lens.
Its too late to change it. Just get used to it - a 840mm lens no longer means a lens with a focal length of 840mm. It means a lens with the same angle of view that an 840mm lens would have with a 35mm image frame. This makes things especially confusing when the same lens might be used with a full-frame or APS-C size sensor. You can blame the journalists (so tedious to always say 'equivalent') or the camera manufacturers (what would sell better 5-100mm or 25-500mm?), but it isn't going to change things.
It is rather like using equivalent MHz as a CPU speed measurement unit.
But the point is that these smaller cameras can have amazingly small angle of view. Smaller than almost any DSLR lens. You can get a camera which has the same angle of view as an 840mm lens on a 35mm camera, and it will resolve more detail than than many older full-frame DSLRs (in the right conditions).
In good lighting conditions these can take excellent pictures. A DSLR will take better pictures in less well lit conditions, may focus more quickly and more accurately, and may take more pictures in quick succession. And a picture taken in good conditions with a long DSLR lens might resolve more detail than a good small camera. But there is not very much in it - and a small camera is certainly easier to carry around and handle. (And in Kuwait in daylight I expect the lighting conditions are quite bright).
With a small sensor you get a greater depth of field (for the same angle of view and aperture). But you get greater problems with diffraction - some cameras reach the diffraction limit at f5.6, so stopping down does not improve the image.
I am aware of medium and large format in addition to 35mm. But they were (are) always relatively specialised, and people who used them know what they are talking about and dont buy things based on meaningless paper specs, unlike many of the people who talk about 35mm equivalent focal length.