Exactly. I think a lot of Christians stick to the "it wasn't slavery, it was indentured servitude" line because they know it is immoral. And, having a supposedly perfect set of moral instructions from a supposedly perfectly moral all knowing being that supports an immoral act like slavery is more than a little problematic for their narrative.
But, they tend not to dig any further. Indentured servitude is also immoral. It is still slavery. Indentured servants were still beaten. It is not like this is a good system, to place people into debt slavery. It is a problematic system prone to exploitation, well beneath any idyllic perfect morality.
Furthermore, the bible sets up the rules for both indentured servitude and slavery. Hebrews could become indentured servants, but foreigners would remain slaves FOR LIFE and passed along as inherited property. The distinction between the two classes of slaves is outlined in Leviticus 25.
Leviticus 25:39 ‘If any of your fellow Israelites become poor and sell themselves to you, do not make them work as slaves. 40 They are to be treated as hired workers or temporary residents among you; they are to work for you until the Year of Jubilee. 41 Then they and their children are to be released, and they will go back to their own clans and to the property of their ancestors. 42 Because the Israelites are my servants, whom I brought out of Egypt, they must not be sold as slaves. 43 Do not rule over them ruthlessly, but fear your God.
44 ‘Your male and female slaves are to come from the nations around you; from them you may buy slaves. 45 You may also buy some of the temporary residents living among you and members of their clans born in your country, and they will become your property. 46 You can bequeath them to your children as inherited property and can make them slaves for life, but you must not rule over your fellow Israelites ruthlessly.
So, it supports BOTH indentured servants AND slaves.