No. A 3 word address is a conversion of latitude, longitude coordinates (commonly referred to as GPS). A 16 digit lat,long coordinate gives you approximately the same level of precision as a 3 word address.
what3words is much more user friendly than GPS coordinates, which means that in practice - when people rather than machines are trying to communicate precise locations - a 3 word address can be more accurate because the people using it are less likely to make mistakes.
When you try to find your current location on the what3words app, it relies on the GPS connection on your device. Your current location, as determined by the GPS on your device, is then converted from lat,long into the 3 word address displayed on the screen. Depending on the performance of the GPS chip on your phone, sometimes your current location may appear to be in a slightly different place to where you actually are (just as is the case on other apps with maps and a current location indicator), or your phone will give new results for your 3 word location when you have not moved as the GPS reading updates (again, just as happens on other apps when the "blue dot" for your current position moves even when you are standing still).