Can a non-EU national enter the Schengen area via Croatia during the COVID pandemic travel restrictions?

Doubtful.

Below is the full text that probably reflects the IATA statement. You will see that there is a bit more to it than just making a booking.

Assume that the Schengen Border Control will be looking for proof that you have been in a risk free area for at least 14 days. Then they will be looking for proof that you are a resident of one of the exempted countries (which the US Citizen is not).

Travel restrictions aim to reduce the number of travellers entering the European Union. The aim is to restrict the spread of the coronavirus and protect public health within the EU, as well as to prevent the virus from spreading from the EU to other countries.
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The following categories of persons are exempt from the temporary travel restriction to the EU+ area from the third countries which are not on the list agreed by the Member States:
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(b) third-country nationals who are long-term residents under the Long-term Residence Directive or deriving their right to reside from other EU Directives or national law or who hold national long-term visas, as well as their respective family members.
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THIRD-COUNTRY NATIONALS
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2. If foreigners who do not hold the citizenship of an EU/EEA Member State or the aforementioned countries nor have regulated stay in those countries want to enter the Republic of Croatia due to:

• Business reasons or economic interest of the Republic of Croatia – it is necessary to present documentation proving the business reason for visiting the Republic of Croatia or the economic interest of the Republic of Croatia, such as an invitation to a meeting of an economic entity from the Republic of Croatia, proof of a board membership, proof of ownership or co-ownership share in a company registered in the Republic of Croatia, documentation on the agreed business obligation with a natural or legal person etc.

• Tourist reasons – it is necessary to present a confirmation of paid accommodation/reservation in one of the accommodation facilities in the Republic of Croatia (reservation, lease contract or lump sum payment of a camp, permanent berth contract in a nautical tourism port, etc.) and

• Education - it is necessary to present a proof of education / studying (e.g. index/student ID, certificate of an educational institution, etc.)

These persons are not subject to a quarantine / self-isolation measure if they present a negative PCR result of a nasal and throat swab for SARS-Cov-2 at the border crossing point, which is not older than 48 hours (counting from the time of taking the swab to arriving at the border crossing point).

If third-country nationals have a test older than 48 hours when entering Croatia, they will be allowed to enter Croatia, however, they will be obligated to self-isolate and re-test themselves in Croatia at their own expense. The above can be applied to passengers and crew members on yachts.

Persons who do not present a negative PCR result are subject to a mandatory 14-day quarantine / self-isolation measure.

Sources:

• Coronavirus 2019-nCoV Q&A - Croatian National Tourist Board
• Travel and transportation during the coronavirus pandemic | European Commission