No.
I wrote an article about this if you want to read my full thoughts, on the topic:
https://www.divetech.com/post/are-full-frame-cameras-worth-the-cost
But to sum up, it would be very hard to determine a quality difference between a full frame camera, and a cropped sensor camera. This past 6 months, I had on loan from Nauticam & Reef Photo, both a Z50 (cropped sensor camera) and a D850 (full frame camera.) I challenged anyone to tell the difference in final quality between the images taken with each. At one point I had set up an online quiz for this purpose, but could never make it work the way I wanted. In trying to set it up, I pulled 20 shots from each camera. I was the photographer who actually took the shots and I couldn't tell which shots were taken with what camera.
I can all but promise you, you will spend ~$4,000 more on a full frame setup and not get $4,000 in additional quality over a cropped sensor.
I have two issues with this.
One, in your linked blog post, you said "[FF] is not worth it." That is a totally subjective statement. It totally depends on the person and their budget. I think it would be much more fair to the reader to say "FF will cost you a lot more - maybe $4500 for your initial setup. And the resulting camera rig will only be slightly more capable." It seems as though you are not disputing that a FF rig IS better/more capable than an equivalent (in terms of modern-ness of the tech) Cropped sensor rig. It's just that it's bigger, heavier, and a lot more expensive. It IS better. It's just that it's only a little better, but a lot more expensive.
And, two, your challenge to identify which photos are from a FF versus Cropped is not fair at all. Clearly, you CAN get completely professional quality images using either platform. The relevant question is, will you be able to capture some images with FF that you would not be able to capture with a Cropped sensor? (meaning, capture them at whatever minimum level of image quality you require) I think the answer to that question is yes. If you have a FF rig, there will be times when you can capture an image that is just barely of acceptable image quality for your desired purpose, where, if you were shooting a Cropped sensor, trying to capture the same image, you would not be able to (at that same level of quality). Of course, this presumes the rigs being compared are of comparable quality. E.g. a really old FF rig might not do as well as the latest and greatest APS-C rig.
If you want to do that comparison, I think you need to use both camera rigs on the same dives, and capture the same images with both. Then see if people can compare the results and tell a difference. I will bet a lot of people WILL be able to tell the difference. Unless you really cherry pick which images to put forth for comparison.
If you're shooting a 100' wreck with ambient light, a FF sensor will probably produce better results. If you're shooting any subject where you want to shoot wide open to achieve nice bokeh, the FF sensor has more potential to do better.
I could be wrong about this one, but I think if you're shooting into the sun, and you're really stopping the lens down to make a nice sunball, the larger sensor will let you capture better images of a close subject - especially if it's not close enough to illuminate with a strobe, or if you're having to use your strobes on full dump even with a FF sensor.
I used to shoot m43. Now I shoot FF. Even with FF, I am rarely able to shoot at ISO 100. I am often shooting at ISO 400 on FF. Shooting a smaller sensor to capture the same image would mean even higher ISOs - which inherently means more noise in the image (presuming equivalent levels of modern-ness to the tech - e.g. both being "latest and greatest"). A m43 sensor with the same megapixel count as a FF has 4 times the pixel density on the sensor, and it's capturing 1/4 the amount of light. It is GOING to have more noise, to capture the same image. Crop is not as bad a multiplier, but it has the same issue.
I'm not a professional, or even an expert, so take my thoughts with a grain of salt.