Why the TBM-4 Avenger was an incremental refinement

How much of an improvement was the General Motors TBM-4 Avenger over earlier TBF and TBM variants?

Probably an incremental improvement, though the passage gives no component list or performance figures.

The TBM-4 belongs to the existing Avenger family rather than a separate aircraft generation. General Motors production could incorporate smaller changes learned from earlier TBF and TBM variants. No specific systems or performance figures are given, so this passage does not support a quantitative comparison. This was a block improvement rather than the later-generation design represented by the Fairey Spearfish.