Think of it this way, you have the option of using a team of surgeons that have been doing their craft for a combined 100 years versus a team of surgeons that have been doing it for 5 years. Who do you think has the steadier hand and the proven ability to perform under pressure? The 5 years have experience and some skill I'm sure, but you'll go with the team with 100 years of experience all day over the others because they've seen and practiced it more.
The K/T/G package has experience in the backfield but no way near the level of experience our starters or backups would have, simply because they are focused on performing in that role every snap at practice where the others are all coming from the defense and running that package a handful of times a day.
Look, Lamb knows the game waaaaaaaaaay better than me, and I trust him. I'm just speaking form my limited experience compared to his. I'm all for risks, but this is an unnecessary one from my perspective. I don't see what these guys offer that our starters don't already have in spades comparatively.