Ian, it is quite common for 'people' to pick a record as you say because it appears to be the only one, perhaps even with slight variation in both surname / first name that fits the time frame or location.
Scotland's people is very good at providing detailed information for the records they have, however as is very common many records either no longer exist, are illegible, or have been transcribed badly. No currently available other record does not mean that the 'chosen' record is in fact the correct one.
I run into this situation regularly not just on WT and not just with Scotland related profiles.
Sometimes it is possible to research the person from another angle by looking at other family members.
Records for a person's known children can often provide additional information about their parents or other family members. Sometimes a will, often baptism records that show the family in a previously unexpected area.
Using different databases can sometimes provide clues as many records can be interpreted/ transcribed in more than one way.
Often it is not possible to establish certainty because there just aren't the detailed sources needed to do so. And we have to accept that the records and the level of detail required for certainty are not available.
Often I add Research Notes that say something like, possible parents are A and B, or they could be A and C, or, or possible spouses are .... or this person is probably not related to the profile because...
Sources can be both reliable and accurate without being correct for the person profiled.