When under extreme conditions, some bacteria will form endospores to protect themselves and become "deactivated". Benzyl alcohol is a bacteriostatic agent, which "stops bacteria from reproducing, while not necessarily killing them otherwise". Without "sterilization" (not disinfection), endospores may still be able to reactivate when the correct conditions are met (body temperature) and cause infection. Certain bacteria are highly resistant to common disinfection procedures and can be deadly if allowed to grow, e.g. Clostridium botulinum, Clostridium tetani, Geobacillus stearothermophilus.
Also, besides sterilization, depyrogenation is also very important in producing anything you gonna inject into your body and should be done simultaneously with sterilization. Pyrogens are the main cause of people having fever/flu-like symptoms because it is also resistant to a lot of chemicals like IPA. In order to remove pyrogens, prepare your bottles with a high heat (constant 260 °C for two hours, without preheating) or bleach or hydrogen peroxide (both need high conc.).
This is simply a precaution to minimize the risk for the sake of one's health. It is all a matter of probability, but you are the one who will decide whether to take the risk with your own body
Bacteria looks like it's the far easier problem to deal with, since Terminal Sterilization cures all failures to control living bacteria.
The main issues left I see to advising "just throw the vial in an oven at 160c for 2 hours" is verifying which compounds besides Test can withstand this temp, and which stoppers are compatible. Chlorobutyl stoppers is what USP advises compounders to use for injectables getting Terminally Sterilized because it's more heat resistant, but Bromobutyl stoppers seem to be more common in UGL because they're slightly cheaper.
Dealing with pyrogens/endotoxins is gonna be the harder nut to crack. They exist on any non-sterile surface. The longer the state of non-sterility, the more endotoxin bacteria leave behind.
They can't be effectively filtered out usually..
The way pharma deals with this is aseptic processing, keeping everything sterile so endotoxins are kept to a minimum in the finished product. Compounders are allowed to "brew" using non-sterile products, but there's a time limit from how long the ingredient becomes non-sterile that it can be used(hours). UGL raws are often non-sterile for years, so the endotoxin content (the "bioburden") must be huge. A mountain of bacteria waste.
As you pointed out deactivation takes really high product destroying temperature.
There might be another way though. There's work being done that demonstrates not all endotoxins are as dangerous as others. The worst of them might be deactivated at lower temps. If that's the case, something like 170c for 3 hours could Terminally Sterilize and deactivate the endotoxins we need to be most concerned with in one easy step.
And anyone who doesn't give a shit, thinks real men thrive on a little dirt in their gear, or believe it's all a FDA/big science hoax, can keep on doing what they do.
No one's trying to force you, unlike the tough guys who demand this discussion get shut down.