The FTDX-101D/MP would be an SDR, simply because it uses software to process its signals, just like most radios have done in IF-DSP for the past many years. Yes, an IF-DSP radio is a superhet, but it most assuredly is an SDR as well. The only question is whether either or both of the FTDX-101D's receivers and transmitters are Direct Sampling types.
I posted the following paragraphs over in the Software Defined Radios topic, and it probably is worth repeating here...
"
I suppose the truth is that hams as a group have not agreed on what an "SDR" is. Is that typical menu-driven superhet radio from 5 to 20 years ago an SDR? I think so, if it has a microprocessor that is controlling modulation, demodulation, IF bandwidth, uses DSP for signal processing, etc. Maybe it might be considered old, and have "out of date" DSP technology, but there is nothing that can take away its SDR label. The radio's characteristics are defined and adjustable by software, and that is the purest definition of a Software Defined Radio.
RTL-SDR dongles and SDRPlay RSP's, etc are SDRs but none of them are direct sampling. They are superhets with RF tuner/downconverters ahead of their A/D converters.
The newest crop of SDRs is different, though... for example, the Flex-6000 series, the Icom IC-7300 and IC-7610 are SDRs all right, but they are also so-called Direct Sampling SDRs, with Digital Downconverting Receivers and Digital Upconverting Transmitters. (They are not superhet receivers). Direct Sampling is the newest technology rage, although I think the performance benefits might be hard detect in many cases.
SDR was a big step that changed how we use radios. Direct sampling is a big technology step but the improvement in the radio performance is harder to detect. For example, a possible future Direct Sampling version of a K3 would probably more or less look and act the same as a K3 does today. Maybe a bandscope would be included, but in truth, you don't Need to use an SDR to do a bandscope, it's just easier and cheaper that way.
73, Ed