If I remember correctly you had a timeframe in which you had to build your house back when they introduced housing - dont ask me how long that was though, thats what... like 3 years back?
Since its stated on the website differently now, I would assume they got rid of that and there is only the 45 day counter in place!
Hope this helps to settle the confusion - its just outdated information that you have a second timer to build your home!