[cphajduk]

The article may be an oversimplification, but your comment is an equal oversimplification. There are many environmental conditions that need to be assumed when comparing reactivity.

For instance, if you have pure Titanium, pure Magnesium, pure aluminum in a vacuum at room temperature and proceed to introduce oxygen, you get the following reactions (simplified elemental chemical reactions, the Enthalpy of formation is what is important here):

Ti + O2 -> TiO2 (Std. Enthalpy of formation is -945kJ/mol)

Mg + O -> MgO (Std. Enthalpy of formation is -601kJ/mol)

4Al + 3O2 -> 2 Al2O3 (Std. Enthalpy of formation is -1675kJ/mol)

As a result, aluminum is most reactive, followed by titanium, then magnesium.

This is the reason why aluminum is used in solid rocket motors and various other explosive devices.

Under different conditions, these numbers may change: for instance a reaction with water instead of air may yield different enthalpies. At quick glance in water, titanium is actually least reactive when compared to aluminum and magnesium.

[A_D_E_P_T]

You can make a general benchmark assumption, e.g. in the Reactivity Series:

https://en.wikipedia.org/wiki/Reactivity_series

So from a high enough vantage point, Ti is very slightly less reactive than Al, less reactive than Mg, and not too far from Fe. A far cry from being "a streetwalker" of a metal.

[phenol]

to make a fair comparison here, you need to normalize per mole of metal. these enthalpies of formation are reported per mole of oxide, but there's twice as much Al per mole of Al2O3 than Ti in TiO2.