Agreed - the return from maintaining a portfolio of 10Y Treasuries will certainly be different from that of a 10Y bond held to redemption. I wasn't seeking to describe how to forecast the former - as you say that it more complicated.

The publications referred to above include varying levels of "sophistication" in their forecasts. The core building blocks are similar, but it's impossible to write a short article like this without leaving out a whole load of interesting detail.

In practice of course, forecasts will be too high or too low. It may have been instructive to add confidence intervals to these forecasts; e.g. the 10Y return from equities is 6.5% pa (plus or minus 5% pa with 90% confidence) but then we would get into a discussion of the return distribution of 10 year returns, which is a fascinating discussion, but a different topic altogether.