You've stumbled upon the truth in actual practice yourself!
Editors are not always the best of musicologists. Some jobs are farmed out to other individuals, 'accredited' I'm sure, but not really qualified for the work on the piece at hand.
If I recall, some of the Schirmer Chopin (nocturnes) had wrong notes in them! (This from years ago - but when engraving is involved, the cost of a correction is high, and often run after run will go out, the errors not removed or corrected.)
This is not uncommon, that an editor facing the intuitive choice of a creative genius will say, "That can't be! They must have meant ___ and not ____," and then had the pluck to alter it, usually going with more academic textbook model theory, and most likely working from sundry older editions vs. manuscripts.
When the Frank Gehry / Walt Disney music pavilion opened, conductor Esa-Pekka Salonen and orchestra members discovered, because of a much clearer acoustic, that players parts for Ravel's Daphnis et Chloe were peppered with wrong notes, not agreeing with the score - that possible because parts to be extracted from the score are often farmed out to other engravers on staff, or outside copyists. (Twenty experts working on something together for twenty days will make twenty mistakes - a known phenomena.)
The Bach / Gounod Ave Maria has an added measure due to Gounod relying upon a less than perfect Bach edition. "(found in the Schwenke manuscript and the Simrock printed edition based upon it, but not in the other Bach manuscripts or the scholarly Bischoff and G. Henle Verlag Urtext printed editions.)" ~ Wiki - reliable enough here :-)
A score is a clear set of directions of what the player is to do, often phrasing and the slight accenting of groups indicated, as you have mentioned, in note-beaming. I rate the differences between not correct to correct as critical.
And if you want frugal, just recall that truly frugal is to initially spend more on quality for something which lasts. If you are going to own and use that edition of the complete Haydn sonatas the rest of your life, the paper and the binding of the Schirmer are infinitely inferior to the physical quality of the Henle. The Schirmer will tear and wear more readily, and become brittle and discolor more rapidly, too: the binding is much more likely to come undone as well. Purchasing the Schirmer three times in your life (may you live long and healthy) becomes More Expensive than purchasing the Henle once.... You have a common misconception of 'frugal,' at least where the purchase of sheet music is concerned.
There is no price one can asses to put on the amount of time it takes to undo a mistake repeated for months on end. The way our brain works learning things, it takes about twenty times of both effort and time to undo something wrongly learned once it is learned incorrectly. To find at the last minute before an exam or performance that something is incorrect and needs to be changed is harrowing, no matter how quickly you may adapt on the fly.
Best regards.
P.s. "top-rate performers of their time," especially of the romantic era and early 1900's, were loaded for bear with distorted later accumulated affectations, fashions and mannerisms of their own time imposed on earlier repertoire. When they edited earlier music, those later era affectations and manners are often found on and in the score: they should be regarded as period documents which include the fashions of the era in which they were edited, not musicologically correct editions of earlier music. (Arthur Rubenstein -- no less great than he was -- if playing Chopin now as he did, would probably not get past the first round in the international Chopin competition, ticked down for 'mannered' playing and too much rubato.)
The point made about Schirmer editions and contemporary composers working with the editors is more than valid, but that more than likely precludes the existence of a Henle edition in the first place :-) The dover editions are also known to have errors here and there, more a matter of a slip of the engraver than distorted editing, and again, though good, lesser quality paper.
P.p.s. Worry only about what is the best edition, with the least errors or later era mannerisms varnished on by way of editing. If you were really worried about people 'making fun of you.' you wouldn't be so diligently pursuing classical music and performance ;-)