So, the whole point of "lagering" is to let the yeast finish working at cold temps to clean up diacetyl and other off flavors and to create carbonation. It's supposed to be a process where the yeast are still working, even going as far as adding active yeast (kruasening) to the lagering tank. If you are not doing that, there's really no need to lager except to clear the beer and "round out" some flavors. Rule of thumb, 1-2 weeks for 1.050ish beers and 4-6 weeks (maybe 8 ) for anything over 1.065.
Quite simply, you don't need extended lagering if you arent following traditional lager protocol and you may be missing out on fresh beer.
I think it really depends on what your goal is. Just a week or two ago, I had a brewer stop by who brews at a small regional brewery in Bavaria, and he ribbed me quite a bit that our Maibock wasn't lagered long enough.
And if you're filtering, you're rounding out flavor and removing yeast in one shot, then the only thing you need to worry about is diacetyl and other ketones.
Of course if you follow this pseudo-accelerated schedule, other things will need to be adjusted as well, for instance hop bitterness. Many lager recipes are formulated with the idea that the beer will be lagering for 5+ weeks and the hop level is adjusted accordingly.
Can you make tasty lager following the traditional German schedule? Absolutely, I walked around the breweries in Aying and Andechs and was absolutely blown away by the "freshness" of the beer, the softness of the malt, and the overall complexity. And the beers are in tanks for well over a month before they are served to the public. Can you make tasty lager following an accelerated schedule? I think you can, but you have to balance a lot more variables.
Frankly, on the professional level, I have a lot of motivation to follow an accelerated schedule. But if I were still homebrewing, I would most likely follow a more traditional path because you have the time to spare anyways.