Is this an exception to the rule that strong acids/bases always replace weak acids/bases?
Every reaction is considered reversible to some extent and feasibility of a reaction is mainly dealt in the terms of favourability of either products or reactants. When we say that creating a weaker acid from a stronger base is feasible, we actually mean that the equilibrium favours the formation of the products in such a case. However some other factors can be at play and can well influence an equilibrium. One such governing principle is Le Chatalier's.

$$ \ce{H2SO4 + 2NaCl &lt;=&gt; 2HCl + Na2SO4 }$$

Here's a youtube video showing the production of hydrochloric acid under laboratory conditions. Notice the $\ce{HCl}$ produced is a gaseous product, and hence there's an imbalance in our equilibrium; $\ce{HCl}$ escapes out as vapors from the solution, lowering $Q_c$ of the reaction thus making the reaction go forward.