Ah ok.
Don’t get me wrong, TVHeadend is not especially friendly, but having used it for a number of years before Channels I’m used to its quirks.
… I’m not sure I could make it through one evening of sighing from the other half if a channel took 8 seconds to load/change. 
I don’t know exactly what TvHeadend does, in terms of how it processes or skips errors/junk, but I’ve tried what I would consider to be a like-for-like with a manually crafted m3u channel (direct from sat>ip) into Channels, then the same via TVHeadend first before into Channels and HD channels are always noticeably faster. I would say this is comparable to what I remember from a Sky+ HD box… although it has been a few years!