Inadequate cooling after refilling of Window AC

Yes, Refrigerant Leaks might be one of the reasons for your AC not cooling properly. If an AC is working low on refrigerant, the probable reason is, either it might have been undercharged while the installation or it is leaking. If it is leaking, then simply adding the refrigerant is not going to solve the problem. The technician has to fix and repair the leak, then immediately go testing the repair, and only then go ahead with charging the system with the exact and required amount of refrigerant. What you need to know is that, the efficiency and performance of any air conditioner is optimum only when the refrigerant charge is exactly matching the manufacturer's given direction and specification. It should be neither undercharged and nor overcharged.

And yes, leaking of Refrigerant is also harmful for the environment.

As far as the question remains if the mixture of gas and air would make the compressor explode, it is evident from your situation that it didn't. What is restricting from the AC from cooling properly is not following the specifications given by the manufacturer. So you have to follow the manufacturer's instructions and only then this problem can be addressed.

It seems the Refrigerant Leaks is causing the unit to not properly cool. Also the technician didn't properly handled the proportion and maintenance of the unit. And that is the reason behind this mix of air with gas leaked into it.

You current option is to dismantle the unit and take it to service center. You can get this repaired in the premise as well. Based on the current technicians handling it doesn't seem like it is done properly. So it'd help to return the unit for servicing. Ask them to test the unit in their own premise for day or two to check the leak.

Freon is primarily used in the AC's. There are few other gases too. However the form under which these gases are used in AC, they don't become immediately flammable. However they require certain process to get flamed. And they convert into phosphate and in turn gets exploded internally. However, the current leak shows the gases are not getting flamed. So don't worry about it. I'd suggest to take the unit to the service center and ask them to fix the leak and adjust the proportion of the gas.

There are many reasons for the improper cooling of the Air Conditioner. It has been observed that ageing affects the AC just like it does with other appliances.

Your case seems to be a little different, though. You have not mentioned whether the repairs have been undertaken by the authorised service centre. If not, please consider referring your AC to the authorised service franchisee.
It looks as if the mechanic has not undertaken the repairs as per the standards of AC manufacturer.
Other reasons for improper AC cooling could be -

1. Air filter clogging - Get it checked. Clean or replace if needed.

2. Refrigerant insufficient - Make sure that the mechanic has filled the enough quantity of the refrigerant. Also note whether the correct refrigerant has been filled.

Furthermore, it would be advisable to consult the manufacturer or their authorised service centre for taking up the repair. They may be in a better position to tackle the issue in a better way.