As argued by a poster in District Dave's forum (someone who is I believe is involved with the Central Line on the technical side), this is only for a very short time:
WTT67 has a 32 minute burst of 105 second headways, which is a rate of 34.3 TPH, or 34 TPH in round figures. But this is not sustained for an hour.
It seems that LU has also highlighted that there'll be 79 trains in service, but this is only for a period of about half an hour - and given the end to end time on the line it is clear that as the 79th train enters service, the 'number of trains' will reduce again as it ends its run through the main part of the route.
So it's all typical 'railway' spin...
Paul