At first glance, it seems as though this is true. In modern commentaries the overriding opinion, therefore, is that Mark here inserts a number of traditions about words of Jesus in an episode about the parables.1 And each element within 21–25 is then said to have its own background. For example, Schneider2 works this out for the passage about the lamp (4:21). Supposedly Mark gives this an interpretation that is somewhat later than the interpretation in Q (in which the word is applied to Jesus himself and not to the gospel). However, there is an inner coherence that exists between verses 21–25 and the preceding passage (see “What Is the Outline of Mark 4:1–25?” under Structure and Outline). Swete3 also prefers this inner coherence. This is important for the exegesis. Brief statements that use very little specific figurative language (lamp, measure), can easily be explained in divergent directions. However, the exegesis of 4:21–25 has to be guided and directed by its coherence with 4:1–20.4
21 And he said to them, “Is a lamp brought in to be put under a basket, or under a bed, and not on a stand?