Using interlaced output from a HTPC is generally not recommended.
You'll most likely deinterlace twice, once in the HTPC, then the HTPC will interlace it again, and the TV will then deinterlace again. This whole process does not ensure that the original interlacing pattern will be reproduced on the TVs end.
Those interlaced modes are really only useful if your TV does not accept progressive for some reason.
Anyway, they are only renamed options. 29i/30i were present before, which are the same options just with another notation.