I haven't read Saito's books, or looked too deeply into degrowth as a movement. I just read this article and thought it made some good arguments against what it claims are Saito's understandings of Marx. I'm not sure I agree with everything, but I thought it was interesting enough to share.
Why would socialist reindustrialization necessitate the exploitation of the global south? You can just cut back on the egregious stuff (ooh spooky degrowth...), substitute with the next best thing (transit electrification instead of car electrification for example), develop more sustainable technology that completely replaces the previous unsustainable one (sodium batteries instead of lithium), or at worst work out a mutually beneficial deal with a foreign country (like the GDR and Vietnam with coffee).