Wrong advice.

0.175 Ohm "maximum" is not maximum over the environmental parameters, it's maximum due to the variation between sold units, and **rated at ***junction temperature* of +25 degC. Or as the datasheet says, "Electrical Characteristics @ Tj = 25 degC (unless otherwise specified)".

Rds_on is *significantly* dependent on die temperature! Fig.4 shows that at Tj = 100 degC, Rds_on is increased by 40% from the given +25degC value. This brings the "maximum" to 0.245 Ohms @ Tj = 100 degC. **This** is the value you should be using in your calculations. Once you actually calculate the die temperature, you can reiterate the calculation.

Note that Tj will be ambient temperature PLUS power dissipated times total Rth_Junction-to-Ambient.

Total Rth_Junction-to-Ambient will be Rth_J-C + Rth_thermal_interface_material + Rth_heatsink. Rth_J-C is given in the datasheet.

It's good to note, unless you severely overspecify your parts, that it's quite normal to run power MOSFETs roughly around Tj = 80 .. 110 degC.

This is why, for first order approximation, you should be routinely multiplying the datasheet front page Rds_on(@Tj=25) by 1.4 or 1.5.

And obviously, for design work, use the worst case numbers (maximum) instead of "typical". But that only covers the possible unit variation.

Using a bit higher gate voltage than what the Rds_on was characterised at, helps, but not by a lot, if at all; they have already done the characterisation at a high enough gate drive to get good numbers.

With such miniature load, Tj says pretty small and the FET easily takes the dissipation regardless of any small calculation error, but this is massively oversized part for the application. 0.016W dissipation heats up the junction by just 0.016W * 62 degC/W = 1 degC even without any heatsinking at all. Still, getting the process and calculation right helps when your next project involves more power.