title: Why does `conda update --all` not update all?
body: <p>Similar to <a href="https://stackoverflow.com/questions/48217641/conda-update-all-not-updating-spyder">this question</a>, but there's no answer there.</p>
  
  <p>I installed <code>anaconda</code>, and then <code>conda install -c conda-forge geopandas</code>. When I ran <code>import geopandas</code>, I got</p>
  
  <pre><code>&gt;&gt;&gt; import geopandas as gpd
  anaconda3/envs/gis/lib/python3.7/importlib/_bootstrap.py:219: 
  RuntimeWarning: numpy.dtype size changed, may indicate binary 
  incompatibility. Expected 96, got 88 
  return f(*args, **kwds)
  </code></pre>
  
  <p>So, I tried updating all packages of my Anaconda env like <code>conda update --all</code>, but that didn't solve the warnings. What <em>did</em> solve it was updating the specific package: <code>conda update numpy</code>.</p>
  
  <p>So, my question is: what does <code>conda update --all</code> do, that it doesn't update all packages?</p>