Why does trihaloacetaldehyde formed during the haloform reaction not undergo a Cannizzaro reaction?
Albeit haloform reaction is primarily for methyloketons, aldehydes which have relatively good leaving groups connected with carbonyl (like chloral), or get it during halogenation, indeed also react.

Here we have another factor limiting usage of Cannizzaro reactions, as although intermediate tetrahedral anion (6) could in principle undergo this reaction if $\ce{R = H-}$, it doesn't if there's a better leaving group then $\ce{H-}$. The point of haloform reactions is to make them if they aren't present already.



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