Is my understanding of this level shifter correct
The only reference to "100mA" that I find in the datasheet has to do with electrostatic discharge limits.

I think you need to look at the section titled "Recommended Operating Conditions" on page 5:



"Pass transistor current" is what you are looking for.   It says 64mA.  So, you are allowed 64mA through each translator.

You really shouldn't get that close to 64mA.

Consider a typical translator with pullups to 5V on one side and 3.3V on the other side.  If you use 100 ohm pull up resistors, you will get 50mA through the translator when the 3.3V side pulls low.  Any normal pull ups (10k to 100k) will have much lower current, so you shouldn't end up in a situation where you hit the maximum current.

What you do have to watch out for is if one (either side) is actively driving a high signal while the other side is pulling a low signal.  Those conditions might get you more current through the translator than allowed - and make your driving circuit unhappy as well.

The datasheet goes into some detail about what to do if you have active drive signals rather than open signals to deal with.