That means it is a very bad idea to use an oversized power supply.
The opposite is true, the problem is almost never the miner itself but the PSU or the other electric components, the miner itself is self-controlled and the likely hood of it heating to the point of melting is just slim to nothing, it will shut down if one of the fans stops and/or temps go above a certain degree, it's probably more likely that the neighbor's cat breaks into your garage and drops a candle on the miner than every protection on the miner itself failing.
By under-sizing PSUs you will risk overdrawing from it, it's a lot safer to run an oversized PSU than not, and the PSU is less likely to fail or catch fire when not being fully loaded.
Now in my humble long experience with miners, whether my own gears or places I used to manage, I can tell you without a doubt that at least 80% of fire incidents happen to "loose connections", most miners that catch fires are those that use wires instead of direct connection to PSU's busbar, and most miners that catch fire are used, tight connections are everything in electricity in general, the un-plug/plug process takes away from the ability of the connector for firmly contact each other, so you have a used miner that changed hands (God knows how many) the connectors were unplugged 5 times before, you unplug them 3 more times, now they are pretty loose and ready to catch fire.
Both the male (PSU side) and the female (hashboard side) will become less secure, so even if you bought a new PSU the female connectors on the hashboard are still bad, if you google search for burned miners/rigs, and you pay some attention to the burnt components assuming they weren't totally fried, you will always see that the melting starts at a connector, not near the fan, not in the middle of any wire.
The "loose contact" also applies to the power cord going into the miner, the copper pins on the PSU need to "click" into the power cord, with continuous use/heat and bad quality, those on your C19 or C13 or whatever will widen and won't click-tight on the PSU pins, that's also a fire hazard.
One way I test this is by gently pulling the miner from the power cord, you will feel if it's holding tight or not, a good cable and a good PSU will stick together like glue, you will need to apply a good amount of force to separate them if you can unplug it easily, then there is something wrong.
15% of fires happen because of sizing issues, PDUs/sockets or wires being sized smaller than they should, a breaker that can handle more than a cable can, maybe a sudden drop in voltage, the miner doesn't care it will still draw the same watts even on a lower voltage, which means more amps to travel in wire, resistance goes up, so does heat, the wire is getting really hot, the mcb/fuse thinks everything is fine so it does nothing, and then fireworks.
I had a main MCB catch fire due to an unbalanced load on 3 phase system, the natural wire was sized with the assumption that there would be a smaller load on it than the load on the live phases (which is how a good system should be), but when one of the phases is out, the neutral will carry the amp difference, so that's also under the section of sizing issues.
5% of fires happen for other reasons that are probably beyond my knowledge,
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I'd say, as long as your MCBs are smaller than the max capacity of your wire given a large voltage drop, and your connections are pretty tight everywhere, you will be safe, keep in mind that everything needs to be as tight as possible, I can't stress on this enough, many professional electricians I know are obsessed about that aspect, in fact, some of them will come back after any installation to re-tighten everything because when the wires run warm for a while they might expand a bit, then they shrink a tiny bit and now they are no more tight, so after they do their expansion and shrinking that happens due to heat and sparks, they tighten them again.
