What you explained is correct.
The ‘thinner’ pour is allowing the concentration of organic/inorganic solvents surface area exposed to vacuum to be lower, allowing the slab to actually form without getting too runny. But its conditionally based off the terpene concentration in the end extract, and lack/presence of residual fats/waxes
If your material is too terpy or columns are too cold (typically a combination of both) you may end up with mother solution that has too low of a residual fat/wax concentration other than the cannabinoids and terpenes themselves.
As others stated, you typically want a warmer temperature to actually keep some of those plant fats/waxes.
If you run it too cold you will nearly ALWAYS run into too high of a terpene concentration to allow for formation of a stable ‘slab’.
A slab is really just the sapy resin/waxes forcing the cannabinoids and terps to remain trapped in an thick sapy oileoresin ‘slab’…
If ran too cold, the lack of residual resin waxes/fats, presence of terpenes and potential butane residuals (thick pour) will usually leave you with formatuon of a cannabinoid lattice structure otherwise known as ‘sugar’…