The whole reason you lager a beer is to make a light, crisp, tasting beer. If you've ever tasted yeast or beer with a lot of yeast in it...light and crisp doesn't come to mind. Leaving the beer exposed to a large yeast cake kind of defeating the purpose of lager process.
I do agree that short periods of time on the yeast will not make a difference. How long or short that period is can only be predicted by that batches yeast health. Nice healthy yeast 5 to 6 weeks you I think you are fine. Even if you are racking to secondary some yeast is still getting transferred.
I'm just not willing to risk leaving an entire batch of beer on top of a large yeast cake guessing it's longevity. So, I primary to completion, rack into a keg, then lager.
The home brewers that are winning lots awards every year. Rack off the yeast before lagering.
BYO Magaizines 10 keys to great lagers.
7. Use a two-stage method of fermentation.
Even with a hard boil and the use of fining agents, protein trub will still make it into the fermenter. Racking a beer from a primary fermenter into a secondary fermenter or lagering vessel eliminates this additional protein. It also removes the yeast sediment, which can result in yeasty characters and off-flavors if it is left in contact with the beer.
With a healthy fermentation, an adequate volume of yeast for conditioning remains in suspension within the beer even after the sediment is removed. Most lagers really develop their clean, finished character through an extended conditioning period of several weeks at temperatures on the low end of the yeast strain’s performance range. Racking into a secondary fermenter allows this process to take place without creating any off-flavors or aromas.