It may indeed seem odd, but it is only odd to people who come from countries where railway travel is much more regulated (usually because trains are once per day or fewer (eg much of the Amtrak network in the USA) .
The Swiss rail system (and the vast majority if public transport) works on an ‘honesty’ system. You are expected to have a valid travel ticket or a pass of some type and as long as that is the case you are free to board a train, bus, lake boat etc; if and when a train controller turns up you will show your ticket and it’s all good. In Switzerland it is very rare for seat reservations to be necessary on most of the rail network, but because the Glacier Express acts like one of the types of train cited in my first sentence you do need a reservation.
My quick guide to the Swiss Travel systesm:
The Swiss railway operating/timetable concept – a quick guide
Switzerland’s railways are a lot different to very large countries in many parts of the world, such as USA and Brazil.
Passenger trains run very frequently on a dense network, so that the rail network operates like a whole-country version of the transit of a large metropolis such as New York.
This means that it is not necessary to reserve seats in advance or buy additional tickets except on a very small number of specific special services.
It also means that short connecting times between trains are worked out so that they are easily possible, even with luggage.
The operation of the national network (aka Swiss Travel System) is by what is called the ‘taktfahrplan’ principle, i.e. that trains run at the same times past each hour at least every 1 hour on most lines, and half hourly where necessary, and all services are programmed to interconnect with each other at nodal points with a minimal connecting time. This minimum connecting time is built in and is designed to enable you to continue a cross country journey without waiting for ages between trains if you have to change trains.
Within this concept, ‘freedom type’ rail passes such as the Swiss Travel Pass and Saver Day Pass (and Eurail Pass) act in the same way as 24 hour pass tickets on many city transit systems around the world, in other words they allow ‘hop on hop off ‘ travel on all the main modes of transport which make up the Swiss Travel System – federal railways, private railways, post buses, city buses, city trams, local railways, lake boats.
It doesn’t matter which type of train you get on on the main national network (which includes all SBB, BLS and private railways).
Train classifications decode can be found on the electronic version of the Swiss National Timetable, as can timetables for each railway line in Switzerland
Home page: http://www.fahrplanfelder.ch/en/welcome.html
Explanation of symbols: http://www.fahrplanfelder.ch/fileadmin/fap_explanations/pdf-Dateien/2022/Zeichenerklaerung.pdf
Train types lexicon: http://www.fahrplanfelder.ch/fileadmin/fap_explanations/pdf-Dateien/2022/Zugcharakterisierung.pdf
Also take a moment to think about how much time it actually takes to change trains at a small and medium sized stations. Short connecting times between trains are worked out so that they are easily possible, even with luggage. Taking 7 minutes as an example. This might not sound a lot of time but think about how far you can actually walk in a straight line in 7 minutes. At an average walking pace even with luggage most people can cover about 700 metres in 7 minutes, which is far further than the distance needed to walk between platform of connecting trains at most Swiss stations (really all except Zurich HB)