Water is a “chemical solvent”. So is alcohol (ethanol), which is in nearly every cough syrup.
In fact, the solvent they used is extremely closely related to commonly used and acceptable solvents, namely propylene glycol (and polyethylene glycol), which you likely consume often. The issue is that (di)ethylene glycol has most of the useful chemical properties here, while generally being cheaper. This has happened often in the past in fact: products meant for human consumption that called for propylene glycol have had that replaced by (di)ethylene glycol as a cost cutting measure and that has lead to cases similar to this.
The real problem is cost cutting without safety checks and oversight, not “chemicals”. The article even says as much:
It advised regulatory agencies to increase surveillance and diligence within the supply chains of countries and regions likely to be affected by the products.