meaning of MOSFET "linear region" in the context of switching losses
&quot;Linear region&quot; in the answers you quote is used somewhat loosely.  Often we say &quot;linear region&quot; or &quot;linear operation&quot; in electronics when we mean in-between operation where a voltage is kept somewhere between the power supply rails (as apposed to clamped to near one of them) or a device like a transistor is kept in the middle region where it is not fully on or fully off.  Often devices aren't all that linear in this &quot;linear region&quot;, but it's a name that stuck from long ago where linear region was as opposed to in switching operation or the clipped region.
It is this middle &quot;linear&quot; region where the device will dissipate significant power.  If the device is a ideal switch, then it can't dissipate power when open since the current is zero, or when closed since the voltage is zero.
This is different from &quot;linear region&quot; when talking about the device physics or details characteristics of a MOSFET.  There &quot;linear&quot; can mean &quot;roughly linear current with applied voltage&quot;, which also means the MOSFET is acting like a resistor as apposed to more like a current source.  That's different from &quot;linear region&quot; from the overall circuit perspective.
Yes, it's context-dependent and can be confusing.  If you need to be precise, use real numbers.