Having concert tickets tracked via a back-end database operated by a concert venue would mean the concert venue could arbitrarily transfer a ticket from one person to another, without the consent of the owner. If there is a dispute, there is no real way for a ticket holder to prove their case, other than their word.
With a NFT on the other hand, a venue could mind a number of NFTs up to the capacity of their venue for a particular concert. Any time the NFT changes hands (is transferred) this transaction is visible on the blockchain, and the buyer can be certain that a ticket was in fact issued by the venue. If a buyer were to buy a concert ticket, the buyer might similarly check the authenticity of the ticket via the venue's website, however unlike with a NFT, if the ticket is for some reason invalidated, there would not really be any way to know what happened, or who was responsible.
With a back-end database, a venue could potentially scam x percent of customers undetected. With a NFT, the issuer cannot scam a customer without it being obvious they have done so.
If you are denied admission to an event, after the fact, if you have an NFT ticket, you can prove that you actually had a valid ticket to the event if you were to complain. If you had an electronic ticket linked to the venue's private database, the venue could potentially deny that your ticket was valid.
Are venues scamming customers in ways you're describing a problem that exists anywhere in the world? Looks to me as if it's mostly a solution in search of a problem.
I don't think it would be possible to know. I know that airlines will generally sell 10x% (100% + x) of seats based on the assumption that some ticket holders will not show up.
The posts you quoted were specifically regarding why a NFT is superior to a back-end database with regards to trusting the entity issuing the NFT. I would expect that cost to transfer a NFT to generally be cheaper than using a back-end database, given that a back-end database will typically involve third-party intermediaries (such as StubHub), which will charge their own fees (which are
very substantial).
There is also the issue of price transparency on the secondary market. It is not easy to know with certainty what others are paying for similar seats when using a back-end database.
There is also a very low barrier to entry into the NFT marketplace. This makes it easier for people to offer competing marketplaces that charge lower fees.