Are we sure Thorpe won't be eligible for a 4th option year? If a player uses all 3 options before they've played 5 "full seasons" as a pro, they are typically eligible for a 4th option.
It may depend on how they handle the 2020 season, since traditionally they've defined a "full season" as 90 days on the active roster, but the 2020 season was less than 90 days long.
Here's further elaboration on the rule:
Most players get only three minor league options, but a player who has accrued less than five "full seasons" is eligible for a 4th minor league option.
For the purpose of determining eligibility for a 4th minor league option, a player accrues a "full season" when he spends at least 90 days on the Active List of an MLB and/or minor league club or clubs in a given season... or (beginning with the 2012 season) spends at least 30 days but less than 90 days on the Active List of an MLB and/or minor league club or clubs followed by an Injured List assignment where the combined time spent on the Active List and the Injured List equals at least 90 days.
By my count, Thorpe may have only had 4 "full seasons" by this criteria, entering 2020:
He played in 2013 but had less than 90 days active (he was in rookie league ball, whose seasons are generally less than 90 days long). Then in March 2015, he had Tommy John surgery and missed the 2015 and 2016 seasons completely, so they don't count as full seasons either (zero days active).
If 2020 counts as a "full season" despite being less than 90 days, then Thorpe would have 5 "full seasons" as a pro and would indeed be out of options in 2021. But if 2020 doesn't count as a "full season", Thorpe should be eligible for a 4th option in 2021.