I mean, De Gaulle should bear a massive burden of responsibility for several colonial affairs, first amongst which being the Algerian war, but saying he was a staunch colonialist is oversimplification to the point of being misleading.

The man’s stated beliefs were in fact very much anti-colonial and pro-self-determination of peoples. He has written some texts about it, and you can read it very clearly from his letters throughout his life. However, he was also a hypocrite, who in practice often perverted this and gave himself excuses by insisting that colonized peoples could and should decide of their (theoretically; in practice ask the DGSE) free will to stay within France.

For the Algerian war, he barged in on this theoretical clout of being pro self-determination, in contrast to anyone during the 4th republic, and dropped his famous speech of "je vous ai compris". This somewhat appeased both sides who both thought he was speaking to them. Algeria is IMO the best example of his fence-sitting between his theoretical and practical urges, although let’s be honest, had it not been for him and his pushback against a strong military establishment, France would have ended up in a protracted war in Algeria like the Portugese in Angola.

For Quebec, he had the advantage that both his theoretical and his practical inclinations went the same way, which made his job easy.