Cleaning vs stripping wood siding for staining

Hi,

Our house has wood siding installed in a rain screen configuration (vertical slats with 1/4” gaps). House was built in 2011, Siding was originally stained with Cabot bleaching oil to produce a weathered gray color.
We moved in last year, and I asked a few painters to quote me on a re-staining job. All painters recommended a bleach washing only, stripping not necessary before re-staining.

I am planning to use Defy Extreme semi-transparent in driftwood grey, and wanted to do a test area first. I started by using oxiclean (mixed according to instructions) applied via pump spray, and noticed that the prior stain came up easily. I used a floor brush to clean (don’t have a pressure washer) in some areas, results are below. 
have I now committed myself to stripping before restaining?

Thanks!