No, not sound good... But they cannot convince him in good faith.
And to give in would be to lie to NATO face.
The problem is that even if he wanted to go to 5%, it is literally impossible to do so, because he lacks the legislative capacity and support to do so.
Let me explain the situation a little.
Sánchez lost the last elections and he governs now with only a tiny margin of 3/4 deputies in the Spanish Congress (he has the Senate against him) and that is only thanks to the support of the all Communist, Populist, Separatist and even pro-terrorist parties in the Congress. Most of those are 100% agains any rise of the Defence Budget, some even wanting to take Spain out of the NATO as soon as possible.
And at the moment he is also beset by many judicial investigations for corruption in his most direct environment, both at a personal level (his own wife and also his brother), and at the level of the political party and government, with several members of the government under suspicion who are gradually suffering "voluntary" resignations for the same reason (corruption scandals)... This very week the #3 of the Ministry of Finance has fallen...
Sánchez has been unable to approve a General State Budget (PGE) in the last three years and has no chance of doing so before the end of the legislature, that ends in 2027. Without PGE it is financially and fiscally impossible to articulate new allocations for Defence, to even reach the mandatory 2% this year he had to siphon dozens of programs from other Ministries (1 Billion € from Education for example) and almost empty the contingency fund, there is no more room for manoeuvre...
Moreover, Sánchez's political survival is not guaranteed. Nobody knows here how long he will be able to stay in power (days/weeks/months). The scandals made public by the media follow one after the other, day after day, each one more lurid and sordid than the last...
We have come to know of the business of his wife family (gay hot-houses and brothels). We learn of operations to blackmail or at least discredit prosecutors and police officers, also of alleged orgies of Ministers in National Paradors... The existence of a huge load of recordings of conversations, watsaps and sms, full of corrupt deals between high ranking government officials... We learn of "professional escorts" placed in state-owned companies as payment for sexual favours...
Oh man... Only this week we learn how they even tried to avoid the seizure of a hard drive during a police search of the home of an ex-Minister of Sánchez (containing allegedly compromising conversations between Ministers and even the Prime Minister Sánchez) camouflaging it under the clothing of a spanish pornstar.
With the corruption scandals continuing to climb the government hierarchy and causing his ‘partners’ to increasingly consider abandoning him in the face of the more and more sordid facts being made public from the investigations...
So no chance of Sánchez acepting the mandatory 5%.
IMHO, if he backtracks in the next few days or weeks under Trump or NATO pressure, it will be a bald faced lie. Nothing more.
Wait for elections or a vote of no confidence to overthrow Sánchez.
Until then, no possibility of Spain going to the 5% to Defence.