They DO have space restrictions, just not as severe as those in a smartphone.
Interestingly, heatpipes in a laptop are a way to deal with the space restrictions - they allow a laptop to dissipate MUCH more heat in a smaller space.
With smartphones, they simply had to "dissipate less heat".
Although I question how much of a benefit this will really be. As it is, even without heatpipes, smartphone thermal throttles are usually set WELL below the CPU's junction temperature limit - the reason is that it's to prevent other components from getting too hot (like the battery). I remember talking to some Sony engineers, and IIRC, the CPU thermal throttle in most Xperia Z family units is not set to protect any of the internal components, but to protect the user's hand. Fujitsu's tricks might actually reduce the junction temperature at which a CPU can operate without burning the user.