That is true if, and ONLY "if", the light is only needed directly below the fixture(s) -- i.e., such as task lighting for a workbench or stationary power tool. But for the general lighting in a typical low-ceilinged garage application, such reflectors are more often actually counterproductive, as they inhibit the wide and even distribution of the light.
I've used those wrapped fixtures before and wouldn't use them again.
First off try not getting your information for fluorescent reflectors from sites like 420.com or HempCultureRus.com. Those reflectors are designed to shed light directly down on a grow bed and they do a very good job of that I'm sure.
Been quite a few years since I've had to access information on Fluorescent Reflectors and was pretty surprised by the results my self. But they have been in use for 20+ years and if any thing the price is coming down.
You need to be careful to select reflectors for the correct ceiling height but they have 98% aluminum reflectors all the way down to 8' ceiling heights for T5, T8, and CFL cans.
And NO you do not need to turn it all on at once.
Task Lighting, 50/50 Switching, or any other arrangement is all possible provided you plan ahead and provide wiring for them before you close the walls. If your worried about "Hauling in the Groceries" and the dim 40 watt bulb in your garage door opener is not enough. Use the dry contacts found on most upper scale door openers to fire a relay that can shed a little more light on the subject. This doesn't need to be additional dedicated task specific lighting but rather can be just 1 or a portion of your garage/shop lighting provided you know how to wire it up.
There are Free Lighting Design, vendor specific, software programs out there on the net and I would highly suggest using one.
http://www.luxart.com/ProdMluxLight.htm
Nothing worse then finishing off the walls just to find out you don't have enough light. Here are some industry recommendations of how much light to use
Activity Illumination (lux, lumen/m2)
Public areas with dark surroundings 20 - 50
Simple orientation for short visits 50 - 100
Working areas where visual tasks are only occasionally performed 100 - 150
Warehouses, Homes, Theaters, Archives 150
Easy Office Work, Classes 250
Normal Office Work, PC Work, Study Library,
Groceries, Show Rooms, Laboratories 500
Supermarkets, Mechanical Workshops, Office Landscapes 750
Normal Drawing Work, Detailed Mechanical Workshops,
Operation Theatres 1,000
Detailed Drawing Work, Very Detailed Mechanical Works 1500 - 2000
Performance of visual tasks of low contrast and very small size
for prolonged periods of time 2000 - 5000
Performance of very prolonged and exacting visual tasks 5000 - 10000
Performance of very special visual tasks of extremely low contrast
and small size 10000 - 20000
Nothing well screw your eyes up faster then not having the correct lighting for the task. And as you can see by the chart, doing close tolerance machine work requires a "Ton of Light". Not having reflectors would just require too many fixtures and doesn't make sense wasting all that light illuminating your ceiling
But then again I know a few girls who like looking at the ceiling ....
