My house is 1870s and the original skirtings (baseboards in USA) are rough sawn on the back but machine planed on the fronts, soi even at that stage we were going the same way as you in terms of machinery doing a lot of the work.
Here we actually started the process of mechanised woodworking somewhat earlier than in the USA (e.g. RN dockyards automatic sheave block making, c.1805), but due to other factors mechanisation across the industry took longer; we didn't suffer the labour shortages which the growing USA did. But mechanisation was still fast enough for a lot of wood plane makers here to have gone under before WWI. There also was somewhat less pressure here to convert to metal planes in site work because the predominant construction type here is masonry shell with timber floors, roofs and fittings - so a lot less carpentry than you get in an American-style timber framed house.
Pretty much the only adjustable metal planewein the UK up until WWI were importeftorom the USA (and presumably expensive as a result). Perhaps because this is because Stanley, Sargent, etc had patented most of what was worth patenting in planes (a bit like IBM was with computers), who knows? AFAIK immediately after WWI the only firm to dip their toe in the water with adjustable planes was Edward Preston, but they didn't make much of a dent. Not surprising, seeing as how they were up against the likes of Stanley and Sargent and later on Millers-Falls. In fact it took trade protectionism after the Wall Street Crash for Record, Marples, Mathieson, Sorby, Chapman, etc to start making Bailey type planes in bulk, and for the prices to become affordable. By that time even medium sized joinery shops had been machine dimensioning for maube 30 to 50 years
But that doesn't mean to say that wven as early WWI anyone in a joiners shop was daft enough to prepare timber by hand, because they weren't. And if all you are doing on site is small works, like shooting in doors, it makes little difference if you use a wooden jack or a metal one. Once it is set up you are good to go. But dimensioning by hand really hasn't been viable for joiners in the UK for more than a century - cabiinetmaking, where the margins are perhaps a bit more generous, may be a different kettle of fish