Highlighted area. . .Why should they. They didn't cause the problem. You choice to install whatever it was you wanted, not MS. Hence, it is your problem What is it that makes folks think that MS should take care of all the problems people create when installing parts or software. MS didn't force you to install that stuff you choice to do so, so you need to take the responsibility.
MS' offer of a free upgrade sends the signal that MS actually wants people to upgrade, and not 'hey, it's totally your call, figure it out yourself'. Some home users will feel that MS' beckoning to upgrade is also MS' pledge that users will be most secure by trusting in MS' calling.
For those who find themselves stuck later on, you are likely to hear them say that MS did cause the hypothetical problems, and perhaps that they thought they were doing the responsible thing by trusting MS' appeal to upgrade as being a promise of experience safety.
To users who understand the free upgrade offer as being made with no undisclosed strings attached (which a 1-time-only install would make for), if it is later discovered that they cannot access their W10 data after a failure, the upgrade offer will likely seem like a bait and switch.
I would agree with that sentiment, and it is only because there is some existing distrusting sentiment by me towards MS, and also general not-forthright commercial practices, that this matter is begging to be questioned.
For the adage of "you need to take the responsibility" to apply, MS' words would need to shift from 'free upgrade offer for the first year' to '1-time-only install offer for the first year'. The words mean different things, and for MS to use one is for MS to need to take responsibility and live up to those words.