My understanding is the same as stated in your original post @Gambit.
I have seen it bandied around that the device will cut out or something if the discharge rating of the battery is too low for the device or the battery heats up too much. In the case of your Sigelei the limit for amp draw is 40A - my logic tells me the Sigelei will allow amp draw up to 40W then. So, for your Samsung 25R, that is above the continuous discharge rating, which is generally accepted as being the rating to base safety on. There is no current standard on pulse discharge rating - some base it on 1 second pulses, some on longer pulses. If the battery overheats should there not be some sort of temperature sensing inside of the device? If so, I have not heard of it.
All in all, I think you are sensible in your decision to stay around 0.4 ohms with the Samsungs if you intend to go high wattage.
I have seen it bandied around that the device will cut out or something if the discharge rating of the battery is too low for the device or the battery heats up too much. In the case of your Sigelei the limit for amp draw is 40A - my logic tells me the Sigelei will allow amp draw up to 40W then. So, for your Samsung 25R, that is above the continuous discharge rating, which is generally accepted as being the rating to base safety on. There is no current standard on pulse discharge rating - some base it on 1 second pulses, some on longer pulses. If the battery overheats should there not be some sort of temperature sensing inside of the device? If so, I have not heard of it.
All in all, I think you are sensible in your decision to stay around 0.4 ohms with the Samsungs if you intend to go high wattage.