True . . .
There is also the question of abundance. It seems more likely life would be found near the thermal jets on the sea floor, but could also be detected as soon as the probe enters Europa's atmosphere. ...But if it is found that a deep dive would be required for a later mission, there would be the matter of transmitting data through hundreds fathoms of both water and ice. The current BLUIE rover could sample eddies of biological waist product, whereas a bobber may simply float for centuries in an isolated bubble of clean ice water.
I think mobility should remain a driving factor.