Age of design
It is likely that the design of a newly manufactured NK-12 differs significantly from the original designs produced 60-years ago. So we are not really comparing the TSFC of an original 1950's NK-12.
Speed
Wikipedia's source for the NK-12 quotes a "TO" figure - presumably TSFC at take-off power.
Wikipedia doesn't identify a source for it's (T)SFC figure for the TP400. The makers of the TP400 don't publish SFC figures.
TSFC increases with speed. Many published TSFC figures are for cruise speeds.
Props
I imagine efficiency depends somewhat on application, and this must include propeller design.
It might be that there are factors other than fuel-efficiency that affect propeller design. For example, noise may not be a factor for most military applications but it would affect civil applications.
Both these engines were designed for military applications but there may have been some difference in prioritisation of these and other factors.
Conclusion
I don't think it has been clearly shown that the NK-12 is more efficient than the TP400 (though it may well be).