I think The Offspring is a good episode but the attitude of the Admiral keeps it from being among the series best for me. The attitude of the Admiral contradicts the attitude of Starfleet for the rest of the series, and as OP mentioned treatment of Lal like a scientific curiosity owned by Starfleet contradicts Measure of a Man.
If you're interested, I have a link to a script of "The Offspring" with some extended dialogue between Haftel and Picard, which personally I would have liked to see. I have no idea whether it was filmed or just existed on paper (and was likely omitted for time), but it gives a broader context to his desire to separate Lal from Data and makes more sense.
If Lal was such an important part in Data's life, why is there absolutely no mention of her here in Brothers? By all accounts, Data should be telling Soong that he is a grandfather and that through Lal, he was able to create genuine emotions.
Well, Data said in "Offspring" that he considered Lal's creation a necessity because he was the only functional Soong type android and her existence would ensure some part of him survived. But he never mentions Lore, and Haftel doesn't either even though his arguments for separation are based on whether Lal could develop in a dangerous direction (something which is more clear from the omitted lines). That Lal isn't mentioned in "Brothers" doesn't bother me because it isn't a huge necessity for that script.