I think you hit the nail on the head. I won't go as far as to call him cheap but he is fiscally responsible to the ownership group and he is the biggest part of that group. I have no doubt he is very loyal and generous to his employees and loves his charities.
All that being said he picks and chooses the part of the baseball operations that he will spend the most on and that has been payroll. The parts of the organization that he wasn't spending spending enough on were the ones you mentioned and international free agency and the scouting , and development processes needed to develop all the young talent whether drafted talent or IFA 16 yr old talent. And you can still see that the Sox are leery of that very young talent when they trade away Nate Jones and $1M their pool money to the Rangers who needed it to sign a 16 yr old :
"Texas was short on bonus pool cash which was preventing them from signing star Dominican OF Bayron Lora whom they agreed a deal with earlier in the month.
Lora was the 3rd ranked international free agent by MLB.com in this past J-2 signing period. The 16-year old outfielder is noted for his power from the right side of the plate and would instantly become one of the better prospects in the Rangers system. However, Texas had a finite amount of international slot money and after signing other amateur free agents including SS Maximo Acosta, Texas was going to have to make a trade to acquire more pool money. https://nolanwritin.com/2019/07/31/texas-rangers-nate-jones-international-money-white-sox/
"In return the Rangers parted way with a couple of minor league pitchers in Joe Jarneski and Ray Castro. Jarneski was a 12th round draft pick of the Rangers back in 2017 and currently is working as a reliever at the Rookie-Ball level. In 10 appearances, the 19-year old had posted a 1.62 ERA and 1.14 WHIP. Castro was signed as an international free agent back in 2016 and was currently with the Rangers Dominican Summer League affiliate. The 22-year old made 9 appearances, 7 of which were starts and posted a 2.02 ERA in 35.2 innings. "
The Sox seem to still prefer older guys like the ones they got from TX. They also traded away pool money to acquire Yeyson Yrizarri, Ryan Burr, Thyago Vieira and Caleb Frare. Also their big signing this year was Yolbert Sanchez who will be 23 this spring in March and just starting off in the states probably at Kannapolis .
All of these things limit your ability to hit on the 16 yr olds who develop into 20-21 yr old superstars like Tatis, Jr., Acuna and Soto or others who turn into very solid big league players such as the 3 16yr olds the Twins got with the international picks in 2009 . Kepler, Polanco ,and Sano. Here's a great article on the scouts and development people and patience it took to get them to where they are now.
http://www.startribune.com/international-signings-in-2009-prompted-twins-rise-into-a-contender/560076992/