First off the Rams are transitioning philosophically from a zone approach where small or non-high-drafted OL can fill roles on the interior to a power/duo approach where physical power is more of a premium. So their previous prioritizations might have changed.
Secondly Boom is gone this offseason, so the Rams will only be paying one OL on this line, that being Havenstein. And Havenstein is a relative bargain for what he provides us.
Third unless a guy like Smith hits FA and the Rams elect to pay him instead, they may just pay Dotson which has the advantage of ensuring the Center position is protected, which means they have some room for error in the draft selection since whoever it is will have studs on either side of him. Which means they can take a brainy pivot which also has the benefit of being ready in a year or two to help a young QB by managing the pre-snap calls.
So signing Dotson ensures the OL is ready to go week one. You know what you have. And also at that point they know they have Jackson a year out from FA at LT, and he is a guy who is let's say "passable" on the blindside, which means it may be hard to determine his worth. Which means by extension that they are probably prioritizing LT if at all possible in this draft. This is not to say it will be there for them at 19 of course. But a best case scenario for the OL would be to sign Dotson and then draft a LT at the top.
That would give us Jackson/Rookie at LT which is very nice. It would give us a great pairing at OG. And it would give us a deep OL with answers for either injury or the future. Oh and who knows... Maybe Bruss returns on top of that and upgrades our depth on the interior.
Now I admit us drafting LT on top of signing Dotson is unlikely. Might even be overkill, but I can dream.