Look at the product website and the primary design criteria was to make an integrated tube amplifier with the footprint of a sheet of A4 (this being the international standard, not far off US Legal).
That is not a design criteria I've seen before, but it tells you who and what this has been made for. Bear in mind that the majority of single Japanese men live with their parents well into their 30s, so think low volume bedroom audiophile.
The other features are, basically, flashing lights (tubes, VU meters). They don't make it sound better, but that's not the point.
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www.luxman.co.jp
I suspect the size limitation has slightly compromised the output transformers, to make them small enough to fit on the chassis, plus quality output transformers don't come cheap (the last pair I bought for KT88, from Sowter, cost almost $1,000).
Luxman's reputation is as one of the very best Japanese high-end brands of supreme quality and failed in the 1980s because they dumbed down. Their main markets are in Japan and elsewhere in the Far East. This product looks great, IAG build quality is top class, it is designed as much for use with vinyl and would most likely be used with 93db+ speakers from Tannoy, Yamaha or JBL, quite possibly vintage, very popular in those markets. The matching turntable is in its 3rd edition and there is a complimentary digital source.
IAG's thinking for this product range seems to be spot on, classic Luxman luxury at an affordable price, based around vinyl. Measurements seem fit for purpose.