With certainty, but the reasoning behind it is beyond mere utilitarianism. It's rooted in classical Ethiopian irredentism. It's important to note that Eritrea never denied Ethiopia access to Assab. It was the Ethiopian's who decided to boycott the use of Eritrean ports after the border war because it would
"hurt Eritrea more than it benefits Ethiopia". Even after the war, Eritrea has repeatedly reiterated that both Massawa and Assab were
free ports to anyone willing to use them. The problem is that Ethiopia (and Western countries) view Eritrean independence as just a historical aberration that will soon correct itself. They've always misinterpreted the situation on the ground by holding the belief that Eritrea and Ethiopia are just two brotherly countries having a temporary conflict. This is oblivious to the reality of how much the two countries have diverged and the amount of anti-Ethiopia sentiment that has been fomenting within Eritrea (ignore the naive "habesha" bromance that you see in the diaspora). Amharic music was banned in Eritrea for two decades preceding the 2018 peace deal ffs. It's why the "one people, two countries" approach that both Ethiopia and Western powers have adopted towards Eritrea has always been destined to fail. In a vacuum, Ethiopian utilisation of Eritrean ports would be a win-win. Ethiopia would alleviate a huge sum from their domestic budget and Eritrea would have a huge revenue stream.
But the underlying issue is HOW that can be achieved. The fact that Abiy hinted at the possibly of a CONFEDERATION with Eritrea during his first "Red Sea" speech was bound to anger Eritrea|ns. Confederation and then unity has always been the ambition of Ethiopia|ns towards Eritrea. At first, this was attempted by enticing Eritrea through economic incentives. Before the deportations in 1998, Eritreans had a crazily disproportionate hand in the Ethiopian economy. Addis Ababa was their playground. Eritreans in Ethiopia were like Indians in Uganda. When war broke out in 1998, the policy went from incentivising confederation, to trying to force it through military means. When they failed in their objective of regime change in 2000, the EPRDF decided to park all their heavy weaponry on the northern border and force Eritrea into a North Korean-esque hyper militarism with the aim of depopulating and demolarising the Eritrean populace into accepting unity with Ethiopia. That however had the opposite effect to what was intended (of which we saw the effects in 2020).
Abiy knows he can't just take Assab without taking Asmara (and Eritrea with it) nor does he want to. There's nothing stopping Eritrea just sabotaging Assab and making it economically unviable as a port. What ship is going to be insured to dock in Assab if there's rockets flying there daily? We've seen how much of a joke the ENDF is in Tigray. And we're also seeing in real time the diplomatic goodwill the trust fund babies of Africa had crumbling in a matter of weeks.
That's why Abiy is now throwing Hail Mary's by negotiating with paper states. So to answer your question, Ethiopia has always had their eyes on Eritrea. However we will need to see if there still is an "Ethiopia" in the coming years and decades to turn that intent into action
