Quaternation sh*t

[meimeiriver]

I have this painting, apa_p_h_acc_artwalll_03. It's slightly tilted, leaning against a wall:

<Pitch>-3.99999809</Pitch>
<Roll>1.63242022e-12</Roll>
<Yaw>90</Yaw>

In ymap, it comes out as:

<rotation x="0.0246776585" y="0.0246776585" z="-0.706676" w="0.706676" />

As correctly seen here in CodeWalker (image on the right). But in-game it appears to be standing straight up:

https://1drv.ms/i/s!AhSxhQ9g_mrMiSfWcmHy7WT5xU4P

Wut?! We're not talking about some infinitesimal rounding error, here: the painting is tilted for 4 whole degrees! (simply -4, 0, 90 does precisely the same, btw). What's going on here?!

P.S. Whoever thought of this convoluted Quaternation sh*t should be taken into the yard and be shot! Nothing but a PITA, and not even working properly!