[basjoos]

It would probably depend on your soil type. The lightweight sandy and loamy soils being less likely to put much side pressure on your blocks compared with the heavier, expand and shrink, clay soils. Also place your rebar pins next to the inside interior of the block so any outward pressure presses directly against the rebar.

Myself, I don't bother with blocks to shore up the sides of my raised beds. I prefer a more flexible raised bed arrangement with mounded sides that I can plant to take advantage of their south and north facing slopes with their microclimates to speed up or slow down crop maturity. This is especially noticeable with strawberries where the earliest berries come off the south facing slope of the raised beds and the last berries comes off the north facing slope. Going block-less also allows you to easily shift the side of a bed if you decide you need a wider path or a wider bed in that location.