@Pintohoo, I see that you recently joined the forum and have not walked a Camino in Spain yet it seems? So welcome and Buen Camino first of all.
Your practical experience appears to be linked to living as a foreign resident in an EU country and to crossing internal land borders. Indeed, compliance with Covid-19 has been largely merely expected of us citizens, without controls at our land borders or the threat of fines. Just as it was the case at the land borders between regions inside a country, for example inside Spain for many months in 2020 and 2021, as you presumably know. Sometimes, when reading forum posts during the past 2 years, I got the impression that international posters could not wrap their minds around the concept of complying voluntarily with legal requirements when they would not be controlled at land borders or when there were no big fines lurking in the background. Such thinking amuses me but makes me a little sad, too.
Flying, ie crossing what is called air borders, whether it’s is an internal international border, for example on a flight from Paris to Madrid, or an external international border, for example on a flight from London to Madrid or from New York to Madrid, is a very different situation in this respect than travelling on a bus from Austria to France.
Are you familiar at all with Spain’s SpTH Health Control Form and system mentioned in the first post of this thread? You may know that filling out this form is still a mandatory requirement for numerous international travellers who fly from a non-EU country to Spain. Without it, travellers will not be allowed boarding in the first place in their home country and even after arrival in Spain they will be shepherded into a dedicated control lane at Madrid airport and can expect random controls of their vaccination documents, as numerous forum members have testified, especially those belonging to the Documental Control category and not to the Fast Control category. You may know that the traveller’s Control category is printed next to the QR code that the traveller receives by email after completion of the online form.